Which expansion did they get right, and why?

[MikkoAkure]

I feel like people often look back at Heavensward with rose-tinted glasses.

It's still my second favorite expansion for many of the reasons people have already mentioned and the elf camping trip arc to get answers from Hraesvelgr was among one of the high points for the entire game. But then there was other stuff people tend to leave out of their nostalgic memories like having to go back to deal with Ul'dah junk, the waaaaaay too long moogle quests that interrupted the main story, the multiple versions of HW Diadem, BRD and MCH being forced to sit still as casters, MCH having a really un-fun RNG rotation and DPS much more reliant on ping, certain Alexander raids were so frustrating that it permanently damaged friendships, Wiping City of Mhach feeling like purgatory upon release since there were so many mechanics that a single person could mess up that could wipe the alliance.

Shadowbringers is looked at fondly IMO for a bunch of reasons. It tightened up the story really well so we weren't split between distinct arcs that broke the flow of the plot. The "cute mascot break" that HW, SB, and EW did here felt more natural and integrated into the plot by having them connected to Urianger and a Lightwarden while the "cute mascots" themselves still presented an element danger. The Scions are finally all present at the same time again with equal screentime and they each received character growth and attention from the writers. The WoL went from a silent hanger-on to more important NPCs who were actually doing the important things to suddenly being the main protagonist who is driving the plot.

Shadowbringers felt like its own game in itself while Heavensward just felt like just another (good) expansion.

My brother who has played way more Final Fantasy games than I have but hates MMOs even picked up FFXIV just to play ARR through Shadowbringers and then quit after he finished it but said the Shadowbringers piece is his top 5 of FF stories.

[Azurarok]

Pretty much this.
People always gush about Shadowbringer's story but I consider it patient zero for the rot that has settled in this game.
As you said it is the reason for every MSQ following a similar template, but it's also the start of the incredibly stagnant job and fight design.

Funnily enough when people say "Stormblood story bad" they always tend to ignore the patch story from 4.2 onward. Building up Garlemald as more than just vague bad guy empire and giving us a glimpse of the political intrigue and factions within it...which was then completely sidelined in ShB and thoroughly destroyed by Endwalker, along with any remaining old lore.

Yeah, as much as I love Shadowbringers they can't just do it again to get the same effect (not to mention they also had outside factors for those sales). I'm also convinced I enjoyed the jobs at the time because it still had traces of what made them good rather than any of the simplifications they've done being actually good. Bozja was fantastic and they missed pretty much every mark on what made it good with Occult Crescent too.

I think they don't have any idea what specifically was good about that expansion and have been blindly tracing its outlines since.

[Destati]

Shadowbringers has the best MSQ by far. HOWEVER, I think Stormblood I feel is when they got the expansion “right”. The story wasn’t perfect and really didn’t get that great until the .x patches, but we had a great amount and variety of content that we just haven’t had since.

• Beast Tribes (or “Allied Societies”) were starting to be viable leveling options, had pretty good rewards and still gave us glam. We also still had the allied quest with a nice reward.
  
• We had a deep dungeon AND [I]four[I] exploratory zones in Eureka.
  
• Treasure Maps and their loot were at their peak (both in the volume of available drops and raw Gil), and thief maps gave us another reason to go underwater.
  
• We still got hard mode dungeons, and two dungeons per patch.
  
• We got Blue Mage, and despite being released late in the cycle, it gave people reason to be out in the overworked again, for a while.
  
• Also felt like we got way way way more emotes in that expansion. Especially at launch.
  
• This was just before they started to really stretch out the patch cycle.

[AlliciaCapulet]

Without a doubt, Heavensward.

Many little things were imperfect, but, at this time, Square Enix were giving things for all kind of players. The casual had dungeons or raid on an easy version, but, could still die and had to do some mecanics.

Extreme and Savage raids were for players who wanted a good challenge.

The big plus :
-Difficulty. In everything, even casual stuff, we could die. We need a stress in a game to be fun, not necessary Dark Soul kind of stress, and HW was still far from that, but it was not a braindead game.
-Difficuly on crafting and gatherer : Old players remember that we needed to farm some redscrip to buy talisman, that was enabling special nodes for a limited time. We needed to gather those to get special mats to craft the raid tier, or the crafting/gathering stuff. Also, each crafter had it's own crafted gear that way, same for gatherer. Those thing were harder to script in a bot, so, there was a lot less of unskilled crafter that uses stuff like plugins or bots to solve the crafting. The recipe were also really hard to HQ, especially without all HQ mats.
-Trinity : Healer were needed and had to heal, tanks needed an healer, and DPS had to dps to pass the dps check.
-Job complexity : They were fun. Think of the Dark Knight where you had to manage your mana to tank. No mana = bye bye tank. Machinist was also way more fun. Scholar had dots, cleric stance and many more attack spells. Summoner had a really nice rotation to play. Since ShB, playing a healer feels the same, and they are not really needed anymore. Their dps rotation is basicly spamming a button. They are now so boring to play, and have an heal kit way too strong for what the game challenge.
-Seasonal events were fun. Lots of mini game to farm to get your reward.
-Relic weapons. Probably one of the best set to do, yes, you need to work for it. Not just farm 1500 memoquartz and voila.

I'll stop here, that's my big plus that the game had back them. There is some low side, like for example this is the first expansion where sightseeing became.... boring. it was fun to do in ARR, and then, I really don't get why they keep doing it with this formula.

[Shistar]

Thanks for starting the thread! Here's what I feel like each expansion got right (I started playing at the tail end of ShB and finished my MSQ shortly before EW would come out, so consider all of this from that lens):

ARR:

• Interesting mech design: It was not rare to see random dungeon bosses with mechanics unique to them (or to be the first ones to have such mechanics). We're talking having to slice the zombie goobue's belly open when it eats someone--and being able to pass the prey tether to a party member--to prevent them from dying, add management in the Wanderer's Palace and some pretty spicy mechs in Pharos Sirius. They don't have the bite they used to nowadays, but I remember wiping when I was a sprout in ShB and thinking damn, this place got hands lol I am sad this is no longer the case.
• The world felt alive and detailed despite its limitations
• They were not afraid to treat dark topics, but they didn't make the whole story about it. An example is sex trafficking (Sastasha), but they don't push it down your throat either. It's there if you're willing to look for it and it's easy to ignore if you don't want to see it. It really fleshes out how Eorzea is not a fairytale fantasy place, it has a lot of dark things under the surface which are fun to explore.

HW:

• They pick up unsolved mysteries and go deeper, connecting dots and giving us new threads to look forward to. Ishgard is rich in interesting lore considering their history goes back over a thousand years and the truth was hidden all this time.
• High-stakes, but still grounded: It's not world-ending, but when we have to run from Ul'dah after being accused of regicide, everyone gets split up and you just don't know what to do with yourself, it's heavy. You sigh in relief when you find shelter with Haurchefant and Ishgard, and again when you start seeing Scions reunite with the group or show signs of life. This was still the time where we were powerful, but not to the levels where we never have to worry about ourselves or our friends. Death was not inescapable or meaningless back then, and losing an important ally was groundbreaking.
• Leaning more heavily into classic fantasy aesthetics: The gothic-inspired architecture of Ishgard is wonderful. We have knights, dragons, a huge (castle-like) cathedral built over the abyss, it's just wonderful for me who really enjoys this kind of aesthetic.
• Dragons, Ysayle and the introduction of Au Ra. That's it, that's all. 10/10 no notes.

SB:

• Boss design became more epic. Susano's sword mechanic, Tsukuyomi's shifting arena, Suzaku's transformation, Seiryu's waves throwing you all over the place, holding onto Shinryu's scales as he takes you far away into a new arena. It's just really cool and you're still interacting with the fight, it's not just a cutscene!
• Hien's EN voice acting was very fun lol and Lyse's funny comments too, though she tested my patience sometimes!
• Au Ra lore, finally!!!
• They pulled at my heartstrings a few times this expansion: Tsuyu, Papalymo, Werlyt (that was horrible, seriously. Do it again.)

ShB:

• Okay, dark elements making a comeback in full force, I see you! I love it when the story is a bit dark, so naturally I liked this expansion's MSQ. Lore bombs everywhere.
• The concept of Light and Darkness not being this clear good vs. evil thing was really, really interesting and well done imo. It's the kind of thing where you only have one chance to get it right and they knocked it out of the park!
• The world is vibrant and beautiful, but isn't afraid to show its broken state. I think the excuse of most of the First being obliterated by the Flood of Light was perfect to keep the whole shard to just 6 areas. I feel like any other habitable shard should be treated like the ARR map and be given more areas.
• Introduction of Shared Fates, it's fun to do with friends as a mindless grind
• Introduction of Amaurot, the ancients, and a huge can of worms that would make the community go insane for a long while (Emet-Selch) lol
• Ryne is precious and we must protect her at all costs. Thancred needs therapy. He always did, but I didn't have an issue with it up until he thought it was a good idea to be mean to the kid in front of me.

EW:

• The grand finale. Grabs all the threads we had lying around and wraps them into a neat bow. If you want to leave here and pretend the game is over, this is the perfect spot for it. Honestly, it doesn't need much more than that to be a successful expansion. I just wish they didn't rush it as hard as they did.
• I did not expect dragons or void lore, but I enjoyed it!
• Loporrits!! I am weak to cute fluffy things. They're so cute and make silly comments. Love the little guys Q_Q
• I feel like some of the most iconic areas in the game are packed into this expansion. Sharlayan was great and gave us so much interesting lore. It was my favorite.
• They finally killed Zenos. I'm so glad lol please don't come back. We've had enough.

DT:

• The sights are amazing. Northern Urqopacha is one of my favorite areas and I feel like they really nailed the vibe they were going for.
• The return to more fast-paced combat from EW was nice to me. Most job changes I really liked. It's not perfect by any means, but it's an upgrade from EW, so I'll take it.
• Mamool Ja lore was very interesting--and horrifying--to me. Especially considering the Mamool Ja boss in Wanderer's.
• Glams are better than ever! Plenty of details, shiny metals, double dyes! There's room for improvement as always, but seeing sneak peeks in LLs is always a treat.
• This is where I would put the housing update, if we already had it! LOL just a little longer... please tell me we're getting it soon... Q_Q

[AstreaLove]

Stormblood & Dawntrail if we're talking strictly encounters.

[Hyperia]

Shadowbringers was great because it did not have a part one or part two split like in SB, EW or DT, but rather, a single cohesive story from start to finish in another world with both new an familiar characters. It gave the devs a nearly clean slate to tell a new story without having to worry about Etherys.

This is what I want in 8.0, a fresh, new story that is cohesive without two different stories in one expansion. Also, make the WoL the center of the story again.

If they really want to be brave, make us the antagonist until 8.5 and then have opinions change about us, if at all. We saved your shard, most of your lives, even if you don’t like that we did it (maybe they wanted to die?).

[Dulcia]

I feel like people often look back at Heavensward with rose-tinted glasses.

It's still my second favorite expansion for many of the reasons people have already mentioned and the elf camping trip arc to get answers from Hraesvelgr was among one of the high points for the entire game. But then there was other stuff people tend to leave out of their nostalgic memories like having to go back to deal with Ul'dah junk, the waaaaaay too long moogle quests that interrupted the main story, the multiple versions of HW Diadem, BRD and MCH being forced to sit still as casters, MCH having a really un-fun RNG rotation and DPS much more reliant on ping, certain Alexander raids were so frustrating that it permanently damaged friendships, Wiping City of Mhach feeling like purgatory upon release since there were so many mechanics that a single person could mess up that could wipe the alliance.

The part I enjoyed the most about Heavensward was the stakes, and how the plot felt like it had consequences. Endwalkers and Dawntrail really feel like there were no consequences for anything that happened. No one in the other parts of the world seemed to care about the plot after the garleans were defeated.

Shadowbringers was great because it did not have a part one or part two split like in SB, EW or DT, but rather, a single cohesive story from start to finish in another world with both new an familiar characters. It gave the devs a nearly clean slate to tell a new story without having to worry about Etherys.

yes! The split in the plot I hate that. I think they do the split in the plot because the 4 Act story is a popular format in japan where act 1 and 2 are reflections of 3 and 4 - but I prefer a story that continues through the beginning and we don't get a moment that goes "and now time for something completely different'

the reason it hurts the stories in 14 is because it takes away time that could have been used to develop the relevant characters. Like Wuk Lamat and Lyse in DT and SB get sped run through their development which left a lot of players frustrated with the characters. compare to alphinaud who gets the pre-heavensward and all of heavensward to develop and learn from his mistakes.

[Barwara]

I loved HW, SHB, EW. The story was engaging and emotional, we had great NPCs we cared about, fought along side or had to say goodbye to, the WOL was able to be the focus of the story but still allow other characters to tell their story, the plot although not perfect was really solid most of the time and it had most importantly momentum, some cutscenes really hit hard and blew me away, there were many overall WOW moments throughout the MSQ… in comparison DT had almost none of that.

[TheDustyOne]

Overall, I'd say Stormblood got it right. Job design had more varied playstyles, combat encounters were more creative, and while the MSQ wasn't as well received, it was still competent, with patch MSQ being a decent high point of the expansion in my mind.

If we're talking story, then Shadowbringers is the obvious choice for an expansion they got right, but that's where the job design started to stagnate, and encounters started slipping with it.