We don't propose badass Luke moments, we want writing that makes sense.
3 Lessons... or was it 1, oh I'm scared of this power. J/k, here's lesson 2 like a split second later. What's lesson 3?
As stated cut for time. Also it could be argued that it ties into the way Rey thinks she can simply recreate what Luke did with Vader in regards to Kylo. While Rey is not aware of the intimate details I think it's easy to see the parallels with Luke being headstrong and leaving Yoda to confront Vader to save Han, Leia, Chewie and Threepio. Rey assumes the outcome of her trying to turn Ben will go the same way, not heeding Luke's advice that it's not going to go the way she thinks.
Is he using the force again when he sees Rey and Kylo touch fingers - I thought he cut himself off from the force. Huh.
Pay attention to the film I say. He re-connects with the Force to reach out to Leia in a previous scene. The movie lampshades this when Kylo and Rey have contact when Rey is in Luke's presence and because he has cut himself off he isn't aware. Then he reaches out to Leia, re-establishing his Force abilities and thus, now able to "see" the contact Rey and Kylo are having.
Luke having a moment of darkness is interesting - but we get like 10 seconds of flashback, and that's it... so under used.
It was established in TFA Luke walked away because of guilt. In TLJ we get the reasons behind it. We get multiple scenes of POV's on the moment and the reveal plays into the themes of failure, hero worship, self recrimination, buying into one's own reputation and self forgiveness so one can move on. And this is how real life is for a lot of people. Maybe it seems small from the outside but to an individual even momentary failure can, bluntly, **** you in Thebes head. With Luke it's a bit more complex still. He struggled as he did in the Emperor's throne room with something terrible and again fought back but instead of being rewarded the universe let it blow up in his face. That momentary weakness shattered his self image, and the fallout riddled him with guilt and self doubt.
Luke cutting himself off from the force is interesting, but it's not explored - like in KOTOR 2, and he comes back.
Uh... Of course he was going to save the bacon at the end. I mean... Yeah.
Luke saying Jedi must die is interesting -- but he goes back on that, and says we have one more Jedi after all! Undercutting his previous lectures for 90% of the film.
Again... Duh. He was in a different mindset at the end then when we first met him in TLJ. It's called an arc.
Luke sensing darkness in Rey, and the mirror scene could have been interesting if it was about some sort of grey-balance, but appears totally unaddressed. Some fun throw away dialog. She goes to the darkness in lesson 1, plays hall of mirrors and learns nothing, and then never addressed.
She learns that her parents, which TFA established she was obsessed with, don't matter. We learn her lineage doesn't matter. That snap moment shows to me that all her actions even in infinite variables all come down to her. Luke's lessons include telling Rey that the totality of the Force, Dark, light and inbetween, don't belong to, or reside in the Jedi or Sith exclusively. And it's certainly addressed by Kylo who uses Rey's feelings after her experience to try to deepen their connection, for as we learn, his own selfish ends.
We don't need Luke running in like rambo, we just need some decent writing.
