My biggest mistake is not doing my homework before joining a league. If/when I see something screwed up, I'm going to point it out figuring people don't want things screwed up. I struggle with the concept of not being able to help those that don't want to be helped.
I am in several leagues where people literally don't even know I am there. So while I am certainly part of the problem, I am not THE problem. I just need to limit myself to non-fucked worlds, which is why my number of teams is steadily declining.