Non-linear gear progression starting at ilv60
The worst feeling in an MMO for me is to have tons of stuff to do but no reason to do it. When leveling, there was always a reason to do something because everything moved you forward. But once you hit level 50, something odd happens where you're given a ton of content, all WAY more fun than the old stuff, but you quickly have no reason to do it anymore.
I'm talking about pretty much every endgame dungeon in the game that doesn't drop gear better than the Darklight sets. There's something odd about me having so much fun running HM Copperbell / Hakkue / Crystal Tower, but having the unique rewards feel like a NQ crafted item you know you'll just replace later.
The reason is, these armor sets are too linear in progression to keep them useful. I really want to hunt for all 3 HM primal weapons, but know it's pointless because Ifrit's is worse than Garuda's, which is worse than Titan's. So because I have access to HM Titan, there is literally no incentive for me to run HM Ifrit or Garuda anymore because their weapon is clearly inferior. There is nothing worse than seeing someone in a full set of awesome Odin/Behemoth armor, knowing they're wasting their time equipping it because it's ultimately useless.
There are tons of threads and reddit posts explaining how this could (and should) be implemented deeply into endgame before FFXIV gets too far and can't do it anymore. As much as I enjoy this game, I can see this really being the only thing that eventually stops me from wanting to log on anymore.
Fun stuff to do, with a linear system of gear improvement that encourages me against doing it. I have no reason to run most of the dungeons i have access too because their loot is useless, and i'm only ilv59.