Agree JJ was in a bad position.
I think it's mostly down to awful planning on Disney's part. The whole story should have been written before any production of the 3 started with competent writers, or at least a general direction of how the films should go should have been planned.
Even if this film was incredible, I would still struggle to enjoy it after the a mediocre force awakens and a god awful last jedi started the trilogy. First time ever I will wait for Netflix / torrent for a star wars movie.