The purchasable pets and mounts were a crass move.
I've played since vanilla, and for a while was a very hardcore raider, but eventually that wore thin. I stayed on because I had friends in the game and we enjoyed hanging out and running the occasional dungeon together, otherwise I would have left a long time before that.
I thought that the cross-realm dungeon finder would be a Good Thing, and I think for a while it was. Back when it first started, people were polite, said hello, etc... then after a while I've lost count of the number of 5-mans I've run through where not a single word was said, but rather a grim race to the end, collect your points and bail out. Then it got worse with the people bailing- "Oh, I don't want to run this dungeon" or the ragequits after a single wipe. Or the meter-sitters bitching that the DPS numbers are too low and trying to votekick people off. The relative anonymity and odds that you'll never see the same people again really brought out the inner asshole.. it got so bad that I eventually refused to group with anyone from a particular server in my realm because they had a reputation of being griefers that would wipe parties for the lols. The worst example was 2 hunters that joined as a group who would go and misdirect the healer, feign, wipe the party and call everyone n-ggers until they got kicked.
I recall being in a heroic Deadmines run, 3 guys were from the same guild on another server, myself and a random from another server. The party leader declared that he was going to boot the lowest DPS before the last boss so he could bring in a guildie for the kill and loot.
Raiding became a chore, and the social structure that comes from it became unbearable. Raiding no longer became a fun thing, but a way of gaining prestige and status on the server. This of course, required extreme dedication of time and effort, and having an "off day" would more than likely result in getting benched and replaced by the dozens of other raiding hopefuls looking for a slot.
The new raid bosses aren't very impressive. Even the Lich King fight was anticlimactic. The Vanilla and BC fights were much more intense. The fights now are pretty much "stand here, don't stand there" positioning fights. Lady Vashj was a pure bitch because of the fight mechanic with the cores, and it was an achievement to defeat her and make it to Hyjal before Blizzard removed the keying requirement to unlock that raid zone.