I found this hot take on Luke's portrayal in TLJ from theforce.net:
"The thing for me about TLJ Luke is that, on the one hand, I understand and appreciate the appeal of a highly dramatic, bold, and unexpected version of "Broken Luke" that we got. I was predicting and looking forward to a Broken Luke for many of the same reasons that Rian Johnson went with the direction: it allowed Mark Hamill to show range, would embrace explanations for why Luke wasn't involved in TFA, and would eventually have to be capped with a reconstruction or resurrection phase. And all those elements were kind of in TLJ...
...But on the other hand, I find the actual plot and execution of the Broken Luke to be fatally weak and, yeah, at this level, out of character because of how the story undermines itself. The story as presented in TLJ embraces far too large of a dimension to Luke's "brokenness" for totally insufficient and badly portrayed causes, ones that end up making the Luke of TLJ seem more self-centered, myopic, and focused on Kylo than I think even the furthest extreme of what Rian Johnson was looking for (as are most of the characters in the Force story.)
When it comes to the hut incident, we're already in very shaky territory with the simple supposition that the Luke from the OT would be creepin' on his nephew, reading his thoughts, and igniting his lightsaber over him; people can, in my opinion, justifiably say that the moment is out of character. It's a subjective argument, but its one that I feel has enough evidence on the side of those critical of the decision that it needs greater explanation. We need to understand what would take the Luke from ROTJ and put him in that headspace, because the basic principles of the scene directly contradict his final form there; why does he feel the need to spy on his nephew, why has he forgotten the evolution he went through, why is he already this broken?
But it's the after-effects of the massacre, the portrayal of his downward spiral afterwards, and especially the way the film interprets and treats the massacre of the school and what the audience is supposed to be focused on that completely undermines the interpretation of Luke in TLJ. The biggest issue is with Luke being so completely broken, arguably to an unbelievable extent, by the events; the film does eventually offer some vagueries that are totally inadequate explanations about him hoping the Force simply creates a counter to Kylo and thus he's trying to stay out of it... but how does that encompass the character from the OT not even telling his sister what happened? Or seeking to die but being unwilling to commit suicide, and for some reason going to a place that is, ultimately, a landmark that Imperial records can locate if need be? How does his mind twist to blame the Jedi? Why is he so convinced that inaction will have a positive benefit? The film's explanation for his breakdown simply becomes one of narrative conveniences and handwaves, depending on the quality of Hamill's acting to carry the story, not internal logic or strong characterization by the script.
But compounding the issue is Rian Johnson's fanboy crush on Kylo Ren again twisting the story. The whole point of the hut scene is supposed to be about explaining how Luke's failure was igniting his saber on some homicidal urges he got after detecting only possibilities about Ben going bad; intrinsic to the scene is the idea that the Ben in front on Luke is still by and large innocent enough that Luke reactions isn't justified. But then the film establishes that Ben, upon leaving the hut, immediately slaughters his school. This is the exact opposite of what the scene should be; because it honestly makes it look an awful lot like Luke's homicidal reactions were justified, and that his mistake was in not finishing the job. That's totally not what Rian Johnson wants to imply, but he was blinded to the issue because...
...The film really, really doesn't want to blame Kylo nearly enough for what happened, or have Luke react in an actually human way, because that way would be against Kylo. All those dead students? They don't really mean anything to the story, beyond explaining why there are no Jedi and where the Knights of Ren (maybe) came from. The script can't conceive of these dead students as living beings that Luke would have loved and cared for, or that Rey should sympathize with, because doing so would require a far more visceral reaction on the part of both of them against Kylo, and Luke's character is not supposed to be defined by wrath towards his nephew but instead a sense of loss and sorrow, while Rey simply can't be allowed to view Kylo negatively in TLJ, no matter how much that makes sense. So whatever element of TLJ's version of Luke isn't wrapped up in melodramatic self-centeredness is instead used to feel sympathy for the school shooter that is Kylo. It's a severe mistake; honestly, the goal of the fill with Luke could have been accomplished simply by having his reaction to the crime send him into such a rage that he's terrified of using the Force because the dark side comes so easily now, or he refuses to train Rey because of the deaths of so many students has wounded him too much.
TLJ wanted to tell the story fo a believably broken Luke trying to manipulate the Force to fixing his mistakes out of some understandable loss of perspective. But what the film actually had in its script was a self-centered coward divorced from any even remotely believable perspective, where his mind contorts in unnatural ways to justify total stagnation and abdication of his responsibilities and previous characterization, alongside the film's virus-like exceptionalism for Kylo Ren."