As someone that has played World of Warcraft since release, I can see why people are flaking out. We're a few months into the expansion and I'm already twiddling my thumbs on nights there are no raids. World Quests are boring as hell, there's only one raid instance, never cared for PvP, and running with randoms is a complete waste of time. The game is sort of like one of those giant bins of Cheese Puffs at Costco. It sure looks like a lot, but before you know it there's nothing left and you're still hungry.
The whole Diablo mobile fiasco didn't help things, that's for sure.