Honestly I don’t think RJ works well with characters he didn’t create himself. He’s probably a far better director without having to deal with a collaborative series of films.
Well, I think he sees himself as an “auteur”, which is fine, and he is very talented, but I think it creates conflicts, when you write the 8th chapter of what is essentially someone else’s story. The Skywalker saga has become a mishmash of conflicting visions, Lucas’, JJ’s, and RJ’s.