I just don’t find it believable, that a man who believed his father could be redeemed, a father who had been a true monster, guilty of the death of millions, would even for an instant contemplate killing his newphew, long enough to ignite his lightsaber, his sister, and best friend’s son, a boy who had done nothing, but have dark thoughts.
Yes, Luke believed his father could be redeemed. It’s also fair to assume that Luke believed he could right the troubled Ben Solo ship.
But it’s important to remember that as soon as Vader threatened Leia, in ROTJ, those thoughts of redeeming went out the window. His fear of losing someone he loved was too great and he reacted with violence. He nearly killed the man he wished to save.
The same goes for Ben, and Luke says why he ignited his lightsaber in the film: “Snoke had already turned his heart. He would bring destruction, pain, death, and the end of everything I love because of what he will become. And for the briefest moment of pure instinct, I thought I could stop it.” It isn’t just dark thoughts. It’s his heart, his future, and premonitions of darkness to come. (Which is believable considering what we have seen from Ben/Kylo so far in the ST. Plus, he killed his master and became the head bad guy, which is something Vader never did). Most of all, it’s a threat to everything Luke loves and, like in ROTJ, he instinctively reacts in fear.
In both cases he’s left ashamed of his actions.
And yes, the future is always in motion, too. Luke didn’t listen to Yoda in TESB. But I think right after he quickly and instinctively reacts over Ben, he remembers that this is his nephew and that the future isn’t set in stone. Unfortunately, it’s too late.
I also don’t find it believable that he would see a solution in exiling himself, waiting to die, while Snoke and Kylo Ren were still at large. It is the obvious choice to try and stop Snoke and Kylo. If Luke fails, he dies, which means he will get his wish of ending the Jedi, if he wins, he can still go to an island to die. So, for me the movie failed to provide a proper motivation for Luke to be so emotionally compromised, that he would forget his Jedi training, knowing the future is always in motion, and raise his lightsaber above a young boy’s head. It also failed to explain why from Luke’s perspective letting Snoke and Kylo run free without a Jedi to challenge them would be the best solution for the galaxy. Had the movie shown that Ben Solo had hurt a loved one, I might have bought Luke’s reaction in Ben’s bedroom. Had the movie shown, that Luke tried to stop Snoke and Kylo, but failed, because he couldn’t hurt his sister, and best friend’s son, and only barely escaped with his life, I might have bought his exile,
What might seem obvious to someone on the outside looking in, may not be so clear for someone who’s right in the thick of it and trying to deal with the immense amount of pain and guilt they carry.
When trying to understand why Luke felt that exile was the answer, we also need to consider the effect this all had on him. Luke’s mistake caused his nephew, his sisters and best friends son, to go down the dark path. It also cost the lives of his students that were all under his care. The level of guilt he felt from this failure is huge, and these are not throwaway decisions, this is something that absolutely devastated him to the core. Or, as Snoke puts it: “split your spirit to the bone.” There is Luke being emotionally compromised.
But, Luke being in exile and his justifications for it are just a cover-up for his guilt and failings. As viewers, we are in Rey’s POV and when she is confused about why Luke is acting the way he is, so are we. The emotions Rey has against Luke are the same as ours. This was intentional, and we are supposed to feel this way. This is part of Luke’s arc in the film.
We have also seen masters make mistakes and go into exile before. So Luke sees the Jedi failing in the past, and now he is repeating their mistakes. The difference is that this time he decides that this Jedi vs. Sith dynamic is a cycle that the galaxy cannot handle anymore. How many lives have been lost in the 60-70 years since the Sith returned? So, to break the cycle he decides that the Jedi won’t participate anymore, and that the Light should rise from another, more worthy source. He alone is taking this burden on his shoulders to take himself out of the game, doing something he couldn’t do in TESB (answering the call of his friends) to allow something new to lift up the light. This is hard for him. In short, he decides that it is time to let the past die.
But, when that worthier source does appear, he doesn’t see her in front of his nose. Or, more likely, he doesn’t want to teach Rey because he doesn’t want her to eventually feel the pain he feels now.
The kicker is that Luke is wrong (like Ben is), and Yoda teaches him why in his final lesson. This was all intentional in order to give Luke a real and solid character arc.
And, to use your example about Luke going to confront Snoke and Ben, I think he knew that it wouldn’t help anything. Ben has been completely betrayed by Luke, so anything he says to try and pull him back to the light will fall on deaf ears. Second, Luke does not want to hurt Ben, nor does he want to give Ben the satisfaction of killing him (At the end of TLJ, RJ found a way around this dilemma). If Luke is destroyed by Ben/Snoke, this will give Snoke the satisfaction that the Jedi have been eliminated and that no new Jedi can rise to fight them. Luke staying alive gives a small bit of hope to the galaxy and puts a sense of fear in Snoke, who is desperate to kill Luke to put his mind at ease.
but TLJ did neither. It just says Luke’s different now, deal with it. That’s not good enough for me. Major character changes should imo happen on screen, not between films.
This seems like something to take up with TFA instead of TLJ. Luke had his major character change before RJ even started writing. JJ is responsible for establishing the change, RJ was just trying to figure out how and why it happened.
I’m not sure if any of this is of any help to you, and it’s starting to look like overkill a bit, but I’m hoping it is. If not, let me know! I love discussions about Star Wars, so if you or anyone else want to chat about it I’m all ears!