Additional unnumbered point: Moving the game in an ever-more-topheavy direction.
i have way more than 5 of them…
I really dislike that we can’t wear stuff that we busted or butts grinding for. It’s soooooooo game breaking. 
Paladins to Horde and Shamans to Alliance. While now I do like my shaman on alliance and Paladin on my horde It feels like that they both lost something being sent to the other side.Mostly shaman though. (If it hadn’t changed I might liked to see Dks on Horde side and Druids on Alliance side.)
Blood Lust (Time Warp) given to mages. The class already provided* a buff, good dps, food, water and portals. Why did they also need to bring the utility buff Shamans did?
Changing to Gun noise. I don’t mind that they added a new gun noise I just wish there was an option in game to change it back.
Focusing too much of the game around Org and SW. Good gosh both of those are bloated.
Destroying UC and Darnassus. Much like the inability to actually change the outcome of the game by being The hero, commander, admiral, leader of your class hall, etc, etc, There is no impact when you can just go back. It is now just a hassle to back to these cities.
This had an impact on both factions’ identity, but Horde both losing shaman exclusivity and getting blood elves really turned it on its head. It hasn’t felt like the same faction since.
1 - Time-gated content
2 - Pathfinder
3 - The War Mode bonus exp
4 - Removing tier set
5 - Adding demon hunters to the game
6 - WoW Tokens
7 - Not banning carry services from trade chat
The Faction Divide
The Faction Divide
The Faction Divide
The Faction Divide
and the Faction Divide
It is literally only a restriction. It provides nothing to the players.
I’m just gonna +1 this gentleman. 
the bfa gladiator mounts were so awful
we earned these glad mounts man
at least they’re easily obtainable by practically anyone at this point with the new 2400+50wins change
which is no where near 0.1%
(glad pre bfa was 0.5%)
THIS TIMES 10 THOUSAND.
How in the world has no one said “xrealm LFR?” Blizz should have merged realms to keep single realm populations healthy instead of this “solution” that destroyed server communities
Changing Disc Priest into what it is now.
Pathfinder in general: Draenor and Legion’s requirements have been removed, would of liked it more if BFA’s was removed.
Paragon Mounts: Whoever came up with that idea should be fired.
AoE cap
Legendary item removal, (specifically Pandaria’s): STILL not being able to go anywhere near Ordos (or even loot him if you happen to kill him without the cape). Seems like a lot of work to remove a long questline for an item.
Giving Sylvanas more plot armor and making a fool out of Saurfang and Bolvar, What the hell was that, Blizz? I’ve seen T-Posing models fight better than that. 
Death Knight Class Hall quest and Rogue Class mount quest: |DK| - Having to go into Undercity (of all places) as Alliance made me quit the whole thing altogether, I think it’d be easier to do if I faction changed to horde for that bit.
|R| - Currently working towards this but I’ve seen the list of targets I have to take out and…oh god that Org AH is going to be a pain to get to, maybe. I just hope it’s not packed at night and I can go and get my birb ASAP. I’m not fond of PVP as you can see.
Edit, added some that I completely forgot about.
by far my biggest issue was when they trashcanned the pvp gearing from MoP/WoD
then the do every single quest in the game and repeat it til you hate 10 rep grinds pathfinder for when you no longer want to play anymore
hated that they got rid of tier sets in LFR (and everywhere else)
hate the borrowed power systems
hate that they got rid of justice/valor/tokens for bad luck protection vendors
Treeform removal. I don’t like the current iteration.
Cascade removal. Should be a H Priest talent or something.
Healing/Spell power removal.
Professions losing their armor enhancement that kept them relevant.
Content removal like the MoP legendary quest chain.
Removing mana from hunters
The SL Enhancement Shaman rework
Demon Hunters
Removing ammo, because most of my guys are engineers.
Ruining AV and ruining SoTA then removing it because nobody wanted to play it anymore.
Bonus:
if they add the non armored version of that dragon for pve means i might be more inclined to be fine with it, especially since this is the case with every glad mount in the game, there´s an inferior equivalent for Normal people that cant get to gladiator.
If they dont however, oh im gonna be so mad, pvp andy arena all day players getting the special mount of the story/environment/pve that they dont give a damn about.
I think is the opposite about bfa glad mounts… blizzard did a good job at separating pve and pvp with bfa glads rewards, just look at this thing it literally have nothing to do with anything pve related of the expansion… its a blood murdering protodrake which also fits the glad theme perfectly, since you stay all day just killing people of other faction at arena…making those totally different vibe mounts for pvp just like the 100 matches mounts should be the ideal for glad mounts.
But instead, most glad mounts are the exact mounts i expect to see as a mount drop for mythic final bosses where they belong.
This one drives me nuts. I have two named accounts… and then WoW 3. Like come on.