Have you ever met children who live without adult care? I have, in Latin America. The notion of Rey raising herself to be a well-adjusted, worldly, spotlessly clean, well-spoken, etc. sans parents in a dog-eat-dog environment is a fantasy more absurd than using our minds to move objects.
I'm not saying people do not rise out of those circumstances, but they do so with a support structure, even if a single caring adult who can transmit the requisite skills, which Jakku conspicuously lacks for anyone.
The onus is on the storyteller to make this seem believable on screen. They present absolutely nothing to suggest she knows how to pilot a vehicle that flies off the ground. She even tells Finn she has no idea how she manoeuvred the Falcon thusly to outfly trained pilots. You can't learn to fight without training partners, full stop. Rey doesn't even seem to have access to a reliable supply of food on screen, but she's in the pink of health. It's all just absurd.
She's a shallow, uninspiring wish-fulfillment character that is actually a major regression for women as action heros. She reminds me of male pulp heroes, who now seem boring and implausible.
