-Wow Anniversaries never felt that special every anniversary I can remember with the exception of the 10th was just an XP bonus tabard sent to you in the mail. Useless if all your characters were max level. The 10th wasn't that special either. A scaled up old raid and a broken 40vs40 battleground. Whoever had more bots or less healers lost and the winner was decided within the first 5 minutes. After I won once and got my title I never stepped foot into again.
-Customer Loyalty. The only thing you get from playing wow for 11 years is if you played since the first month of vanilla you get a statue sent to you.
-They never got the talent system right in wow. The old Trees were a mess and had lots of filler, lots of people googled the best build or stuck with their own build which may have sucked. It felt more like an RPG though and it was a very rewarding feeling to gain a talent point each level.
Mop's talent Grid was a good idea but I think it was poorly implemented. There's often 1 good choice per tier vs 2 bad choices or 1 choice is clearly pve one pvp and one sucks. Some classes got stuck with really boring awful grids like Rogues with no clear theme for any of the tiers except the Mobility tier (60). 2 classes got stuck with a grid where no talents change based your specialization, Death Knights and Rogues.
-Class Trainers were abandoned. Almost no reason to ever visit one unless your a druid and want to change your duel spec.
-Lots of little things(You no longer need firewood to make a campfire to cook with. You no longer buy or craft reagents for your class.) Most people will just label that stuff as "Tedium"
- Over use of Phasing technology for quests.
- No choice of where to level anymore. IF your alliance in draenor its Shadowmoon valley-Gorgrond-Talador-Spires-Nagrand
if your horde its Frostfire Ridge-Gorgrond-Talador-Spires-Nagrand.
- They never attempted to balance Racial abilities. Ever see a gnome or a worgen in Arena? Nope just Humans barring the classes that cannot be Human like druids. Despite what you have heard this expansion in Wotlk Human was also the most popular pvp race because of Every Man for himself and increased stealth detection. Humans have always been popular ppl like how they look but the last time Humans were not a dominantly represented race in Arena was TBC when Arena was first introduced into the game. Simple back then Humans only had an active use detect stealth ability there was no every man for himself.