The elements of what people seem to hate are actually what I liked about this movie. I liked that it smashed the pedestals that the audience places some of these characters on. Luke shows flaws and he himself, in his initial shame and recluse, tries to make realistic some of the hero worship and romantic preconcieved notions that people had of him. He eventually finds the strength to crawl out of his rut and in some ways, meet the expectations people had of him, but not in a grandiose manner where he bitch slaps his nephew down and destroys a squad of AT-ATs. He does it with minimal defense, almost non-violence, thus becoming a symbol of hope yet again. My only major gripe with Luke's portrayal is the brief temptation to murder Ben Solo in his sleep; that was definitely from left field.
As for Rey's Mary Sue tendencies, to me, it goes to show that lineages shouldn't matter, as if one particular bloodline has a monopoly on the force and there should be some kind of force monarchy. It can be anyone.