I just ran out of stuff to do in WoW. I could do more random Troll heroics to add a few more itemlevels to my 355, but I don't want to. Been there, seen that. I could start to grind a PvP set. But I'd start at 0 resilience, which is a bit silly as a healer. Also, healing in PvP never really looked that appealing to me. I did it before on my druid during TBC and WotLK and it was fun for a while to be immortal. But it feels bland to do this now. I could play through the 85 quests, but I can't stand the monotonous combat against the paperdoll enemies; even if the stories are sometimes nice.
It hasn't always been like that in WoW. And although I already know that some readers start to talk about 'burnout' now, I rather prefer the explanation that there is absolutely no context to what I do in WoW. Improving your character was fun for years in WoW, but to improve it outside of any context seems silly. It was fun learning to play the new class and to figure out how to bind keys, but that's done now. I know when to use my different heals and shields. All that is left is learning encounters; no thank you.
In the past there was a community, but there is no community now. WoW doesn't actually put you into any community. Everything is random groups. Sure, I could try to get into a guild. But I don't feel like it. Blame me if you want: I bet I'm no more different than a lot of other players. Why did I play WoW for so many days again? The combat mechanics are top notch; as is the art. Unfortunately that's it. There's no context for my character.
One last word about the Firelands. This is actually rather nicely done. But it doesn't add context, either. I run around on single player mode and can kill anything. The mobs are (finally) a bit tougher in the firelands, but they are still not dangerous in any way - especially not for a healer. How much fun would it be to have huge Firelands with different mobs and stuff to explore, and, yes, items to gain? A virtual world where you could band together with other players and pick your fights? Expand a frontier?
World of Warcrafts's core, the (group-based) combat, is world-class if you manage to find serious enemies. But there's nothing else there; no context for the combat.