As for Rey’s powers it seems to me that RJ has simply changed the nature of the Force for his own convenience. The OT (and even the midichlorian-infested PT) establishes the Force as something that requires serious training and incredible mental/emotional discipline - irrespective of the wielders’ natural proclivities. In RJ’s SW universe the Force manifests like X-Men powers (see ‘Broom Boy’).
I’ll correct you here as that would be JJ Abrams. And as I’ve said, she can pick up powers, but has no guidance as to how to use them. Luke had serious doubts. Ben and Yoda had to overcome his doubts. That is one of my biggest problems with the complaints about TLJ. So much of what Rian did was based directly on JJ’s setup. Blaming these things on Rian is nonsense. Luke’s self exile after Kylo turned and destroyed the school, Rey’s ability to pick up powers as soon as she sees them, the First Order being like the Empire, the Resistance being like the Rebellion, all these things come straight from TFA and Abrams.
She doesn’t need guidance to use them. She lifts a mountainside without effort, kicks Luke’s butt and teaches him hope(!), triple shoots TIE fighters and slaughters Snoke’s guards and even goes straight to the Dark Side on Ach-To without repercussions beyond a mild disappointment. This is all on Rian. Yes, JJ wrote Rey as a…very powerful character, but a) we all assumed actual reasons were pending and b) there has to be a limit. That’s why Anakin and Luke’s powers only manifested as good piloting skills and (in Anakin’s case) some vague ESP. Otherwise you’d have kids Force-choking their parents over petty disagreements or levitating their math teacher. Why would the Jedi Council refuse to train Anakin if it’s apparent that Force powers simply grow exponentially anyway? Wouldn’t that be risking his becoming a Sith lord under his own steam? No, clearly the lore requires some kind of limits as clearly indicated by what has been established over the 6 movies (Midichlorian BS notwithstanding).
And no, Luke’s self-exile did not have to mean Luke’s nervous breakdown. He could have gone to the temple for new knowledge, foreseen Rey’s arrival/emergence, and orchestrated things in a way to break free of the old orthodoxy without having his character reduced to pre-RoTJ levels. That’s on Rian.
However I agree this whole thing would have gone a lot smoother if JJ and Kasdan had actually thought things through beyond their obsession with mystery boxes. Clearly no-one learned from the eternally ridiculous shoehorning of Leia into the twin sister role in RoTJ…