The feeling that I did this myself and it’s good, often beats the feeling that Professionals did this for me and it’s perfect.
— Clay Shirky, Cognitive Surplus
I think we tolerate far more flaws in the MMO genre not just because making massively multiplayer games is especially hard but also because we feel a sense of collaborative development. Players feel like they are contributing something to the game in a way that is not possible in “one and done” games. There is iterative development. There are forums with developers there. There is player-created content. The community participates in testing. It is our game, not their game.
On the other hand, the vast majority of the playerbase is not engaged in the forums, and the biggest game in the Western market has the smallest player input relative to “Professionals did this for me.”
[Update: Alternately, someone has probably worked out the mathematically optimal build for your class. How often do you work through the options on your own, even knowing the math has already been done? How often do you see that theory-crafted build and tweak it, making it your own even though it is most likely slightly worse than the guide-perfect build?]