Nothing Luke says disservices where he ended up in TLJ. “A Jedi’s weapon deserves more respect” - yes, he’s poking fun at his old ways. He changed by the end of The Last Jedi. It’s a meta joke at the same time, but that’s besides the point. Plus, it was fear that kept him there. Fear that he’d fail the galaxy again, fear how Leia and Han would react to his actions, etc.
We are already planning on fixing the Leia knowledge in Ascendant. Especially if Rey is turned into a clone, Leia will begin to recognize the similarities as she trains her. She spent time with Palpatine in the Senate, so she is used to his aura in the Force, even if she wasn’t aware of such a thing at the time. Luke knows because he’s a ghost. They’ve sorta just gained omniscience.
Luke raising the X-Wing is such poetic imagery for how much his character has grown across the saga it would just be a shame to see it gone. Yes, it doesn’t make the most sense that it’s functional, but he did make the right choice by not using it in TLJ. If he had shown up to those gorilla walkers in-person he would have been dead in 10 seconds flat, Skywalker blood or not. His use of the Force at the end of TLJ really can’t be diminished to just a “that was the only way to intervene” moment. It was the most Jedi-like way to intervene. He never attacked, only using the Force for defense.

EDIT: Oh yeah, also Leia knowing that Rey has such a dark history yet still hedging all of her bets into her regardless is the emotional undercurrent of the whole film. She made the mistake of sending Ben away for her brother to deal with, but this time she takes up the reigns herself and her faith and devotion to Rey is what pays off and saves the galaxy. Otherwise Leia does basically nothing for the plot in what is supposed to be her movie of the triology (TFA was Han, TLJ was Luke, TROS was hers).