You are forgetting one thing though Lillith. All of those features you've mentioned there were released over the course of 10 years.
- Sky was released through the first expansion pack from FFXI, namely the "Rise of the Zilart", at the end of 2003.
- Dynamis followed about 3 months after that and wasn't well received at that time. It needed another month or two to expand on it and make major changes to the feature as a whole to make it enjoyable for the players.
- Sea on the other hand was released with the 2nd expansion pack, namely the "Chains of Promathia" (which was released at the end of september 2004, roughly 4 to 5 months after the big Dynamis update). The introduction of Sea also brought along Limbus.
- Salvage, Einherjar and Nyzul were released through FFXI's 3rd Expansion pack, namely the "Treasures of Aht Urhgan", which was released mid April 2006.
- The Walk of Echoes was introduced through FFXI's 4th Expansion pack, namely the "Wings of the Goddess", which was released around the end of November 2007.
- After the "Wings of the Goddess" expansion pack, SE took a different turn by releasing 3 "Battle Add-on" (they were not calling it an expansion pack) in the form of Abyssea, which were: "Visions" (released in June 2010), "Scars" (released in August 2010) and "Heroes" (released November 2010)
- And then finally, FFXI's 5th Expansion pack (the "Seekers of Adoulin") was released in March 2013.
The only reason that the content from the first 4 Expansion Packs remained relevant, was because of the fact that during the lifecycle of the "Rise of the Zilarts", the Level cap was increased from 50 to 75 and then stayed like that for a grand total of almost 7 years. 7 years... During that time, the only form of progression we had, was the horizontal progression, which requires a lot of grinding from the players which would make the 2.x relics seem like child's play. Or even camping NM's with insane spawning windows, which are being camped by a lot of people which would make the FFXIV hunts seem hilariously easy.
FFXI players will feel nostalgic to those days and wish that FFXIV would be more like that, but let's be honest here... Do you still want to grind for months in order to get a relic? Would you still camp at NM spawning spots for hours, waiting for it to pop and hoping that you will be able to claim it before someone else does? Because, back then... If you didn't claim it, tough luck. You won't be getting the drop. Better luck next time.
Times have chanced and if SE would even dare mention that they are implementing these kinds of features, the forums would literally be on fire and even more people would jump ship.
Yes, we all know that people have stopped playing FFXIV due to a "lack of content". Not everyone is happy with every single job the game has to offer, doesn't want to craft or gather items, doesn't want to/can't do Alexander Savage, but that's ok. There is no shame in taking a break and waiting for the next patch to be released.
SE is still working on releasing a patch every 3 to 4 months. However, they took a breather after releasing Heavensward, so 3.1 has been delayed. It will be released around the 10th of November, which is in less then a month from now.
What we know so far about 3.1, is that it's going to introduce 2 new dungeons, a new 24-man Raid, the Airship Exploration (of which its description sounds an awful lot like Sky to me) and add more Main Story Quests. Hard-core raiders who are only interested in running Alexander Savage, will have to wait till 3.2 (which should be released 3 to 4 months after that). But, it doesn't stop there...
We all know that FFXIV didn't deliver what the original team promised their players with 1.0. With 2.x they completely turned it around and build a solid foundation on which they can continue building. They are going to expand on that foundation with the 3.x patch series. The first step they've made was making the zones bigger, introduce flying, the Company Workshop and the introduction of a "Normal"-mode for the 8-man raid. They are working on introducting more types of content for us to play with. The next one on the list is the "Airship Exploration" (which i've mentioned earlier), introduce the "Lord of Verminion" add-on for the Golder Saucer, but also introduce a "Beginner's Hall" (somewhere along the line).
We will get more things to sink our teeth into. "Rome wasn't build in a day". The only question remains: Will you be willing to wait for it?