To me, a good part of what makes a fandom thrives is how varied fics are and how often challenging fics are published. My most-loved fandoms don't seem to have limits, for better or worse. I feel that some fandoms never "take off" because everybody writes the characters more or less the same way and congratulate each other on a job well done. That's always made me leave the fandom.

I'm not an author but I can imagine how upsetting it can be to see what people do with your universe (I don't like what some people have done with my designs) but I don't really understand explicitly inviting people to play in your universe and expecting people to play by some rules (either you share or you don't; it doesn't seem to me there's a middle road).