While I don't see Disney making any horror or gratuitously violent action films any time soon, for the most part with the properties they have bought, like Marvel and Star Wars, the maturity level that each had has stayed the same even if some of the writing on individual pieces of it weren't the best. It isn't like they tried to make those properties full of cuddly anthropomorphic cartoon characters and damsel in distress princesses in need of rescue.
I think a more likely answer is there was too much executive meddling and they just didn't want anybody else creating things under a system that wasn't of their own making even if would have been better than they could have come up with or that it was in large part already done.
