What I didn't like about Mists of Pandaria:
-The asian theme. Sure, it's well done and the zones are gorgeous. But it just gets old really fast. I signed up for a tolkien-like world and now there are pandas all over.
-The lore. I can't bring myself to care at all about any of the raid instances. I don't care about any of the bosses or their history. I find there's just a lot of new characters that don't have nearly as much backstory as Illidan or Arthas.
-The horrible gating of everything behind reputation and the slow rates of Valor acquisition. That made it hell to do on my main, and impossible on my alt without tearing my eyes out. What I enjoyed the most about Cata was the ability to have several characters raid ready so I could switch on the fly depending on what my guild needed. But now with the huge ilvl gaps and the removal of any decent catchup mechanic, my alts won't see endgame content until next expansion if I reroll.
-LFR being considered the catchup mechanic for alts. I've farmed those damn raids for months already, the last thing I want is to do it again.
-Lack of five-mans. In 4.3 I enjoyed running the HoT heroics. I would run them again and again because I liked their lore and atmosphere. But I just don't care about the heroics we have. Not only are there really few of them, they are mostly boring trash packs with the bosses being glorified elites. Makes alts even MORE of a chore.
-Did I mention alts are a pain in the ass?