I agree, Mary Sue is a lame, vague term that I'm guilty of using myself. In regards to Rey, I just wish they explored her immediate backstory a bit more instead of using her as a vessel for solutions and a character focus in numerous setpieces without exploring her nuances or faulting her to require cooperation and assistance. It's not black and white, as she obviously has her moments, but it's an overarching issue (and probably the only big one) I have with the film; it's insistence to push forward aggressively and spend little time exploring our characters intimately or growing them through quiet exchanges. So while with Luke we see him make mistakes and learn a bit about him, his family, and his history, long before and during the climatic setpieces (stuff like Leia bailing Luke, Chewie, and Han out of the prison escape is a good example of the dynamic), with Rey we simply see her often having ideas, running in head first, and taking little time to reach peak ability.
And her versatility makes her fucking rad. I love her. She makes for great cinema, and Daisy nails it. I'm also positive they'll explore her deliberately vague backstory a bit more in the next movies. I like that they kept that a central mystery. But when I hear that in the prequel novel it explores how she has a flight sim salvaged from a wreck, gets screwed over by people, and has learned how to put parts together in her workshop to maximise her investments, I'm sad we saw almost literally none of this in the film. It's quintessential Abrams, similar to Star Trek 2009, where the narrative moves so far and is so focused on the moment-to-moment emotional investment that it doesn't want to breath, just as with young Kirk's incredibly fast, forward moving arc. The different here, in my opinion, between Rey and Luke is that with Luke we do see more justification for his strengths and weaknesses. The Force Awakens simply doesn't bother. Rey is not the only character subjective to this; Finn's motivations are great in theory but still fasttracked. And while I can see how some might prefer this style of film making, it's a strength I feel ANH and ESB had far greater over TFA in establishing and building characters. Kylo is probably the only one to receive a really full spectrum of attention, in intimacy and climax.
As a side, I'm also really disappointed that some leverage the term Mary Sue as instant equation for sexism. I can see where the correlation is drawn but it's grossly inaccurate the moment we admit the term is vague, and unfairly dismissive of discussion on strengths/weaknesses of particular character development and arcs. "REY IS MARY SUE" / "THAT'S SEXIST" is a braindead argument on both sides.
