My beef with the game (and every single other MMO) is the time commitment. I don't want to level up my character to 85 just to get to the content that people actually want to play. If I came back to the game, I'd gladly pay money to just start out at the level cap, or somewhere in the ballpark of it. In WoW specifically, many classes don't get their workhorse spell combos until later in the game, making PvP not even close to an option until you've already sunk several weeks into the game, and with the rework of lower-level content, dungeons don't require any effort until you're almost ready for raiding.
Even once you get to the level cap, that's not the end of it. If you wanna go PvE, you're going to have to run heroics until you get good enough gear for raiding. Then you're going to have to get into a raiding guild and grind out the early-game raids until you get an entire new set of gear, which will take a while because all the higher-ranking guildies get priority on drops since they're part of every single raid, then you get to finally do the endgame content, which maybe you run a single small part of once a week, and other than that it's all about stocking up on food for buffs and other necessary supplies. And then if you decide to switch over to PvP, you have to start from close to the beginning, because PvE gear isn't that great for PvP.
With that said, the World PvP (that is, outside of battlegrounds and sanctioned areas for it) is simply wonderful, mostly because the game is more or less going off the rails. I can feel a quivering in my loins just thinking about how much fun places like Stranglethorn Vale were, getting a couple friends together to ambush some Alliance players, the cat-and-mouse of trying to avoid their level-cap guildmates who they'd inevitably call in to one-shot you, a bunch of guys showing up from Stormwind to kill everything in Base Camp... again... a zeppelin full of Horde guys jumping down to take it back, good times.