More than ever, the game feels like a treadmill, and while that's generally what MMO's are, others do a better job of hiding it by providing more variety. We have the exact same raid cycle of a four-boss 8 man hardmode content, followed by 24 man casual steamroll content. We're still farming DR Ex to cap tomes.
Moreover, so little actually changed in terms of gameplay and systems with the expansion. Square played it so ridiculously safe. Gear have the exact same stats with no interesting new customization options, such as materia melding in dungeon gear, enchants, proc effects, set item bonuses, new equipment slots for perhaps relics or offhands, new stats, etc. Jobs are just the same with 5 new skills, and we still have no customization options. Armory system and cross-class skills feels dated and pointless, when the new jobs didn't even branch off of any classes. Crafting systems did change, but only for the worse.
I'm used to MMO expansions making significant changes to the core game, but Heavensward ended up feeling more like a large patch. I appreciated the story and new zones and flying mounts initially, but that honeymoon period wore off awhile ago.