For me a very big part was #1 (death of world pvp). They pretty much destroyed any means for players to make their own content. You run what blizzard thinks you should run or you do their battlegrounds and you queue and teleport to all of them. None of the dynamic skirmishes and battles that raged in various parts of the world or at instance gates that vanilla (and TBC somewhat) had.
The other major thing they did that killed the game is all of the cross realm queuing and interaction. Previous to them you built up a community on your server. People were aware of was a massive tool or who to watch out for in the world. Players knew who they were playing with or against and the game was better for it. Now you just queue up with a bunch of anonymous people which encourages poor behavior and little respect between players.
All thats left now is the endgame which pretty much means (if you expect to progress well and not deal with pickup groups) that you've got to block off multiple nights a week for raiding or your arena / battleground team. I'm not in college anymore, I don't care for or have time for that.