Poorly balanced classes, no endgame to speak of (while it's technically possible to level to max there's little reason to do so). The only way you'll accomplish it is doing the exact same things for hundreds of hours. Though there are many different skills per class you get limited points and moayt classes only have one or two things that work endgame. Some classes have none like sorcerer. Blizzard has gotten so far and lazy off the profits they aren't even trying. Their solution is make it where leveling is even slower and gear grinding is so rare you'd be lucky to get one usable piece a month after 8 hours a day playing. Needs multiple years and expansions to get sorted out if it ever will.