Because as ridiculous as Crystal Spaceships are, you were hardly surrounded by them, and the rest of outland "Felt" like Warcraft, Draenor, WAS, Warcraft. Pandaria on the other hand, I've honestly felt completely disconnected aside from the tie ins, I honestly couldn't give a damn about the Mogu, Mantid, and other Pandaria Natives. It's not the Darknedgy crowd that's taken over, they're on Diablo. It's the "KAWAIIDESUDESU" crowd that have taken over, and trust me, as annoying as the first group is, the second is much, much worse.
OT: Theme does matter, I absolutely cannot stand the asian theme of MoP, and know quite a few who agree, the game is much better than it was in Cata, overall, but the theme just has me waiting for whatever the next expansion is, so that I can finally leave Pandaria for good and never look back.