OCs can be good, or at least 'not bad' but it's pretty rare these days. I'd rather have a canon poorly written than an OC badly written because to me, OCs don't belong in fandoms, I like to keep original work and fandoms separate. I have had good instances with doubling for one or two people in the past but for the most part, those who make an OC just wanting a good time and to be romanced, are painful to work with. 

Universes like Naruto or Avatar or HP can give birth to some of the worst OCs, so only certain fandoms to me, can house OCs alongside canons without screwing things up.