Just to list a few:
The quality of 6.0's story is debatable, if you want some more specific complaints about it just take a look
here
The post 6.0 story has been mostly filler and forgettable.
Combat gameplay is probably the worst it has ever been, the fixation on everything looping either every 60 or 120 seconds leading to incredibly samey job design, gigantic hitboxes, overabudance of bodycheck mechanics to prevent recovery and artificially inflate the time spent progging a fight.
Increasingly longer gaps between patches, we went from 3.5 months to 4 months to now 4.5 months.
Very short shelf life of the content we have been getting, little to no midcore content or even content to spend longer amounts of time on between patches.
The relic weapon quests essentially auto-completing themselves.
More severe bugs than any previous expansion.
Most people probably don't even remember the bug that would lock you out of your main job mechanic if you had another bard in the party, Shake It Off healing for 1mil HP, the boss aggro and buff cap issues in TOP, your job buffs applying to other people in the party, the housing lottery debacle, the Ninja Mudra bug that lasted for over a month, etc