I don't really appreciate your dismals, given you're not explaining your position at all and are literally ignoring my posts, focusing on aspects that don't address my actual complaint: Rey's inexplicable force mastery.
I never said Ren was as powerful as Vader. I actually explained that he wasn't, and that I liked this aspect of the character. I feel that you're ignoring me at this point. I explained why the audience is expected to believe Ren is a Sith, and you've offered zero evidence to contrary. Simply put: being a Sith requires training in the ways of the force and light sabre, this undermines the credibility of Rey defeating Ren. If you disagree, please explain why.
She wasn't afraid of leaving Jakku, as we see in her excitement at seeing the forest planet for the first time. Rey was afraid of missing her family, who she expected to return to collect her. A trusting, almost noble, position to take, given the hardships we see her endure on Jakku. Loyalty and trust are not faults. In contrast, Luke rejected leaving Tatooine because Owen had drilled it into him that he was a farmer. It wasn't until Owen and his Aunt were killed that he decided to follow Kenobi.
I won't speak for the "Mary Sue" crowd you refer to, but the issue for me with Rey having no faults is that this means she doesn't have to grow or learn. If Rey never fails, and thus is perfect, what character does she have? The closest we see her failing is having to try twice to mind control another person. Of course, as you mention, she is a hero character, however Finn - the the other hero character - has clearly defined faults, and has real development. I like Rey, I mention before I think she's kick ass, I just wish she was presented better. This criticism is smaller than my criticism of her mastery of the force, to be fair.
The issue isn't Rey using the force - nor even that she beat Ren, at least inherently - it's the lack of time, effort and training we see. The simple question is: how can Rey perform a Jedi mind trick, perform telekinesis, and beat down a trained Sith with zero training in either the ways of the force, or a light sabre? The literally decades of training we see Anakin Skywalker undertake are almost meaningless in comparison if all it takes to achieve Rey's level of force mastery is some words of encouragement from a non-force user. This is the issue.