Sorry but this for me is a classic example of someone looking to shoehorn in story elements they wish had been in the film but actually weren't, the idea that Luke is playing the waiting game and building wisdom on his island, the idea that he doesn't actually think Kylo is irredeemable are I think exactly that.
As I'v said before I strongly suspect that the biggest flaw in TLJ might well be studio pressure behind the scenes on Rian Johnson as to me the film feels like its building in certain directions but ultimately cops out on them. I mean ESB back in the day was a brave film, it took our expectations of Luke as a standard "believe in yourself" style chosen one hero and it ripped them up. TLJ recycling elements of Luke's story from ESB and ROTJ is a less effective fashion isn't brave its simply unoriginal IMHO.
A version of TLJ that had the balls of ESB would IMHO have had Luke actually moving away from the idea of Jedi and Sith and the black and white idea of good and evil it represents. We get some small hints at that early on but ultimately the film never backs them up and I suspect the reason is Disney were afraid to turn their backs on the status quo. The whole Luke/Ben story could I think have been so much more effective going that direction(which I suspect might have been the original intension), rather than just doing a poorly setup reworking of Vader in ROTJ with the reverse outcome we could have been shown a different aspect in which Luke failed. He might try and redeem Ben but he's left with a situation where he can't fully remove the darkness from him and rejects him as a result leading to confrontation and his fully turning.
Equally I think Rey's character feels like it cops out in the same fashion. The whole story with Kylo seems to be building towards her joining him yet ultimately she rejects him and the two characters retreat to even more simplistic good/evil positions. Unlike Lucas Johnson/Disney were not prepared to move past their simplistic hero character and in clinging to her they basically destroy much of the dramatic depth the film might have. To me this very strongly smells of marketing men pointing to charts with "strong female character" and "profit" on them yet ultimately by killing the depth of the character I think they've made it forgettable.
Indeed the giveaway is really that the climax of the film isn't about Rey at all, her lifting some rocks is a bad punchline at best with no weight to it that feels like it was written on the back of a napkin. Luke has to take centre stage rather than being a mentor of wisdom because Rey has had any dramatic potential removed.
Honestly I do think you get the sense in TLJ at points that yes Johnson is a skilled director who could have made a quality film(unlike prequel era Lucas or Abrams) but I suspect the main thing holding that back was a lack of freedom in scripting and in feeling forced to carry on with Abrams childish disrespectful meta tone from TFA. Ontop of that perhaps also simply a lack of time in terms of scripting.