Overall the movie is pretty good. Character portraits are fantastic and nothing in the movie betrays the Star Wars
mythology.
But your criticism about Rey's backstory is correct imo. I also found the fact that both Rey and Finn could pretty much match Kylo Ren in lightsaber combat a little weird to say the least, since they never had any training.
I give EPVII an 8.5/10 but it could be a 10/10 if it weren't by the inconsistencies I mentioned above.