That's usually an excuse for people who jump into any online game without a Trueskill system, or an approximation of. I find it more enjoyable to play a game with skill involved against someone with more skill and lose, than to lose to someone who simply put in more time. It's like playing any CCG: the richest player usually has the advantage.
WoW has 10 million subscribers, about the same as subscribers for Xbox Live, all who play games like GTAIV, Rock Band, TF2 and Halo 3 online. Games that require skill (and that's not counting how many of the 15 million steam subscribers play online skill based games, or the number of people who play skill based online games on private servers.)
No, the problem is MMORPGers expect that if they put X amount of time in something then they should win. It's the darkside of grind-based gameplay. It teaches the player that skill means nothing so long as you have a high enough number to throw at it, and you get higher numbers by investing grind-time. While that makes sense in a single-player experience, it's unfair in a cooperative environment if it's taken too far. Working together to achieve a goal (figure out how to overcome a bosses' combat strategy) is a nice way for players to work together and solve problems together, but in a PvP setting it's harder to create that strategic atmosphere. (That's not to say some strategy isn't involved, but when I played WoW you knew the strategies before entering the battlegrounds. It was never dynamic or engaging.)
