Dungeons: the formula has remained the same since ARR and not one single dungeon have even attempted to change this. What I am talking about, part 1: corridor with no to little exploration ability, tank pull every mob until the group hits a wall, group aoe, repeat until this part is done. 2: boss, 3: see 1, 4: see 2, 5: see 1, 6: see 2, and you are done.
Instead of even trying to do something here the devs instead have chosen to make fewer and fewer dungeons each expansion, ARR 3 per patch, HW 2 per patch, SB 1,5 per patch.
Having a dungeon that follows this formula is not bad now and then, but every single time it makes it bad and the dungeon boring from day 1.
Changes to this formula could be changing tha amount of bosses in a dungeon, the number of bosses can in reality be 0-x (x being how ever many bosses the devs feel like putting in said dungeon).
You can add exploration elements with hidden minibosses, hidden rooms, perhaps even have a dungeon with stronger mobs and traps. Just something else then this same old formula. And if someone is thinking about the loot just throw that in at the end.

The raids. Not really raids anymore, instead 4 trials that has to be completed in the right order. The difficulty of these have also gone through the floor, then the basement and not moving in on the center of the world. Perhaps moving away from the usual "has to be primal related" and in an arena toward more open areas that gives groups options when choosing which bosses to deal with first. Oh and also again hidden bosses and difficult mobs along the way. Basically moving away from the current formula.
And ya, I am of the opinion that if I can complete the newest raid then said raid is to easy, I am not only fine with content to difficult for me, I want it since that gives me as a player a reason to improve... now the problem with this in this game is the lack of content that is in between in difficulty, you have super easy (normal content), easy enough to be pugged (raids) and really hard (the ultimate fights), there is nothing between easy enough to pug and the ultimate fight and that is insane.

The early leveling experience post 4.0. Tried to level a new char but the phase in which classes gain skills are not consistent, some gain faster and some slower. Gaining new skills every other level was a good phase. The redesign of the skills in SB was imho a big mistake, I understand not wanting the players to sit with an extreme amount of skills but there has to be another way to deal with this since some classes are still sitting with a large amount of skills, only difference is that now some classes have more skills then others. All classes should have the same amount of skills.

Choices in your characters progression are none existing. Do you get to choose where to spend points in attributes? No, set on auto. Do we get to choose which skills we would like to boost, heck do we get any say in our skills? No, that it seems the devs think is to difficult for players. Do we have a say in our gear? Not really, every 6th month new gear come along and one set is better then the rest.

Customization is limited, the games character creator is not the worse but it could and should be much better, other games that are also on the ps4 manage to have better so no reason for FFXIV to settle with less. Glamour is also limited and choosing the color of your gear is by far the worse, and if they blame this on the ps4 I would like to point toward ESO that let players choose 3 different colors on most gear and that game is also on the ps4.
They should also add more glamour that even low level crafters can make, the mats for these should be easy to get.

Content locked behind story elements, some of which are 8-player content. Oh you can skip alright, if you pay a lot... this here is just greedy, make the story in arr and hw optional so that new players that do not care about it can move to where their friends are faster. As more expansions and patches come along this will be a taller and taller wall for new players to climb, even for players thinking of returning this can be a reason to not return.

The old maps are empty. This could be fixed by having an expansion that opens up new areas in the old maps. Would only work once but it feels like it would be time for that.

This is more rumors but from what they say the engine is limiting, if that is true then I would rather see them spend one expansion on fixing that while not adding new classes or races.

More content please, SB has been a dry desert of content with the devs showing little to no interest in doing more then just below the bare minimum. New kind of content is fine and actually something I would like, it would make me continue playing this game. But that content has to be good and something players generally want. Time for the devs to actually ask the players what kind of content they want and what in current content the paying customers find good/bad/want to change.

I would love if the devs did something that again made me excited to log into the game, but I just don't see that happening. Instead I am looking to end my sub, and before anyone points to the door I would like to say "I know where it is and I am taking my wallet with me" and while 1 person leaving is not a big lose it will be if nothing changes and what is new feels like what is old resulting in more players picking up their wallet and walking through that door while the fanboys scream "Good to be rid of you!".