I don't really want to re-live BFA, but here it goes. From my own experience ofc.
- Azerite Power, not that Artifact Power was good either, but would've hoped they'd learn from their mistakes
- Removal of Legion systems without compensating them
- Outside of raids and M+ you did only world quests, there was no other activity
- War mode was dead most of the time and bugged out the rest the time
- Azerite armor rerolling got more expensive with each reroll
- Content was slower than Legion
- World quests were slower to complete than Legion
- The grindiness of their new design introduced in Legion started to get old
- As a raider, you spent more time preparing for the raid than raiding at times
- Corruptions were RNG at start, when vendor got introduced it was on a rotation for no reason
- Azshara's font and double trinket shenanigans
- Story was meh
- No casual content(still a problem in SL)
- Azerite Armor traits were locked behind Azerite Power levels that you couldn't get before raid released and the grind was silly. Think it was only fixed in last patch
- No bag space to be had(azerite armor took it all)
- Specifically Fire Mage in the end, which didn't work unless you had Font+Bracers+max mastery corruptions.
- Constant lag fests. First day I couldn't do anything for 2 hours, because servers kept crashing and it didn't get better all expansion when huge events were going on
- Islands were boring and you only did them for AP. Even as a Mage you could pull the whole Island and not die.
- Warfronts were also pretty underwhelming, you basically couldn't loose and we never got PvP warfronts
- There weren't many positives to the game. Raid were good. M+ was worth doing past 10 weekly runs.
But at least it wasn't as bad as SL so far, which outside of raiding and PvP was just dead content till 9.2 pretty much when we at least got some content to do outside raiding and PvP. Not to mention the content gaps.