As for the whole thing about Rey defeating Kylo in a lightsaber suel. Aren’t we forgetting that Luke never had any lightsaber sparring training what-so-ever. He learned to block some laser-bolts from a small harmless droid by Obi-Wan, and then he ran around in a swamp with Yoda on his back learning mostly levitation and some Jedi philosophy. Even if you count the novelization or the deleted scenes as canon all the lightsaber training he did with Yoda was cutting a few metal rods throws into the air. I also seem to recall that he didn’t do that well on that test.
Aren’t we kind of judging this film by PT logic? That it’s the moves that count, not the use of the Force. Pre-PT material often put a lot more of a focus on the importance of channeling the Force and fining inner peace and control, which is exactly what Rey did in TFA. A lot of the mystical elements of the lightsaber was lost in the PT, but Kasdan and Abrams seem to have brought it back here.
Luke got his ass kicked by Vader. Then he trained for three more years to finally become a Jedi. Where and how he trained nobody knows, but it’s nice to have movies that don’t spoon feed you everything, and allow you to fill in the blanks yourself. The only relevant exposition needed at the start of Jedi was that Luke’s powers had grown immensely since the previous film.
Even then, Luke wasn’t able to defeat Vader until he used the dark side of the force in their last battle.