I'd rather not see another "virgin birth" thing either, it's probably best to mostly ignore the Prequels.
Your asking people to hold off from forming an opinion for years. They can only go by what's been released so far, which is this story.
The problem is they're making a grand opinion on the same little information. I'm making no solid opinion, I'm giving the story the benefit of the doubt and assuming there's more to tell. This movie's story is over but Rey's story is just beginning! So why all of the sudden leap to any conclusions about her character?
I could be wrong, she *could* turn out to be something of a flawless "Mary Sue" but there's no reason to assume that now based on what little we know, being a third of the way through her story.
So people are wrong to instantly leap to judgements and leaps and logic after this one movie because they have little to go on. It's like turning off "A New Hope" a third of the way through and declaring Luke nothing more than a whiny punk and everyone destined to fail.
Why see a third of the story, make conclusions, and go from there? There's a story being told here and we have a way t go.
To watch this and instantly call Rey a perfect Mary Sue not only, first of all, misunderstands what a Mary Sue is but makes large, radical, conclusions based on partial information.
Why no go neutral? Make no large conclusions and assume the story will play itself out. If at the end of the second movie she remains "perfect", without flaws, or doesn't have some fall from her height they we can make some conclusions.
But there's no reason now to assume she's perfect because she's bested an injured, green, punk with a lightsaber when it's made clear in the entire story there's more to her past than we, and even she, knows.