Arguably the most contentious element of The Last Jedi has been the characterisation of Luke Skywalker. When we last saw Luke in Return of the Jedi he was a triumphant Jedi Knight who had become confident and wise, resisted the lure of the Dark Side and redeemed his father. When we catch up with him in The Last Jedi he's a broken man who has come to despise both himself and the belief system he so strongly embraced in the Original Trilogy. The question is whether this makes sense.
Obviously a lot can happen in thirty years. Over that kind of time some people change drastically. Others scarcely change at all. So how did Luke change, and why? In The Last Jedi, Luke implies that the world he fought for in the Original Trilogy did come into being: "for many years there was balance." It appears that the change began when Ben was born; Luke notably says "I thought I could pass on my strengths." This seems to relate to what Yoda tells him later: "Pass on what you have learned: strength, mastery, but weakness, folly, failure also." This implies an error at the foundation of the philosophy Luke took towards training the new order of Jedi: that it was about strength primarily, particularly in Ben's case of enabling the "mighty Skywalker blood." Perhaps this to a degree explains how Snoke was able to manipulate Ben, because he had been trained to see the Force as a form of strength alone, as power, something Luke was very keen to tell Rey was explicitly not the case.
Is this error consistent with Luke's character in the Original Trilogy? It's difficult to say. In Return of the Jedi Luke certainly used the Force as a source of raw strength, particularly when he called upon it to threaten and ultimately destroy Jabba the Hutt. He also called upon it in fury in the final confrontation on the Death Star, in which he nearly slew his father before realising what the Emperor was doing. It's also true that he never truly finished his training with Yoda, because he left recklessly early in The Empire Strikes Back and only really "completed" his training and became a Jedi when he refused to kill Vader. Certainly Luke understood the value of compassion, and surely would have brought that to his training, but it might be argued that his victory on the Death Star was a combination of his own compassion and the Emperor's arrogance. I'm honestly not sure whether it's possible to conclusively say that Luke might have lacked the overall mastery to train Ben, but it's possible, and he seems to think so, claiming it was "hubris" to do so. Again, however, it may be a combination of circumstances: Luke's own overconfidence and Snoke's manipulation.
Nonetheless, I'd argue that this leaves room for Luke to develop in this way. It seems that the final say on how he lost Ben was a moment of weakness in which, foreseeing the destruction his nephew would cause in the future, he panicked and drew his lightsaber upon him: "I saw darkness. I'd sensed it building in him. I'd seen it in moments during his training. But then I looked inside, and it was beyond what I ever imagined. Snoke had already turned his heart. He would bring destruction and pain and death and the end of everything I loved because of what he would become."
This appears to be highly reminiscent of Luke's rash reaction in The Empire Strikes Back when Yoda tells him he must not go chasing his vision: "But Han and Leia will die if I don't!" Obi-Wan tells him, "You don't know that," and when Yoda reminds him of his "failure at the cave", Luke insists "I've learned so much since then." He hadn't learned enough, however, to prevent him from running off after a vision about which he could not be sure. Yoda sums up the situation as he leaves: "Reckless is he." This isn't just a mistake Luke could make once; it's a consistent part of his character, seen also in Return of the Jedi when Vader's taunting about Leia almost leads to his fall to the Dark Side.
So, was a moment of weakness in which Luke would contemplate destroying his own nephew consistent with this aspect of his character? It seems that way. He nearly killed his own father before feeling pity for him, seeing what he himself was at risk of becoming, and relenting. Furthermore, sometimes people change in some ways but not in others. Yoda remarks upon this in both The Empire Strikes Back and The Last Jedi. In the former, he observes, "All his life has he looked away, to the future, to the horizon; never his mind on where he was, what he was doing." In the latter: "Still looking to the horizon, never here, now, the need in front of your nose." At this point Yoda also argues that Luke failed to pass on the value of learning from failure; I suppose we just have to accept that to be the case, but it appears to relate to his fixation on "the horizon"; he has never been sufficiently concerned with the present, thinking too much about the future and about certain consequences, which is actually a narrow point of view, as it both blinds him to the present and limits the possibilities he imagines. Just as he assumed that Han and Leia would die if he did not save them on Bespin, for a moment he assumed that Ben would bring the galaxy to ruins and acted rashly in response. This is a consistent part of his character.
The next thing to consider is the action he took after this, going into isolation on Ahch-To rather than rectifying the problem he had created. I feel that much of the explanation for this can be found in what Luke says earlier about training Ben. He observes that "Leia trusted me with her son," and "Leia blamed Snoke, but it was me. I failed." He later says that after drawing his lightsaber upon Ben he was "left with shame, and consequence." Luke argues elsewhere in the film that the Jedi are fundamentally flawed, as their actions have led to disaster, but I'd argue that the specific reason for his exile is more personal: he was deeply ashamed of having betrayed Leia and Han, his two closest friends who were also his family, by letting their son fall to the Dark Side. The other source of shame is probably the feeling that he failed to restore the Jedi Order, a responsibility which, after the death of Yoda, had fallen solely upon him. Reflecting upon his own failures and those of the Jedi Order historically, he must have decided that any further action on his part would only cause further pain and suffering and destruction. This would still fit with the "looking to the horizon" mentality; he must have believed that anything he could do would only make the problem worse.
Ultimately I think the characterisation works and is consistent with Luke's character and story, but I can also perceive a few problems with it.
1. Despite the enormous length of The Last Jedi, Luke's character is perhaps slightly underwritten. The audience is possibly asked to read into things more than they should. I think the characterisation works, but should I have really needed to rewatch specific scenes from The Empire Strikes Back and Return of the Jedi to find the most tangible links? These Disney Star Wars films probably need more production time to allow the screenplays to breathe. Also, while I'm sure Lucasfilm keeps a clear eye on the scripts, it may not have hurt to have had a collaborator or two on the screenplay.
2. The entire character arc only needs to exist because of the plot of The Force Awakens, and this leads me to a broader issue: I feel like the problems with the sequel trilogy fundamentally lie with The Force Awakens, and that there was not the time or means for this film to rectify them. If The Force Awakens had been willing to give a clear reason for Luke's disappearance rather than trying to keep the audience hooked with "mystery box" storytelling, there would have been no need for Luke to undergo so many changes in (from the audience's point of view) so little time.
3. This speaks to a wider problem with the Sequel Trilogy in general, which wants to have its cake and eat it too by introducing a new set of protagonists while retaining the old ones. Luke's role in The Force Awakens was minimised because it reduced the viewer's interest in Rey, and this leaves me thinking that, from a storytelling point of view, it was a mistake to have the Original Trilogy characters at all, because they will end up having either little to no character development (which is how Han appears in The Force Awakens), or have to go through too much (which is how Luke arguably appears in The Last Jedi). Yet Disney knows that familiar characters sell more cinema tickets. The film wants us to care about Rey, Finn and Poe, but by selling the films to us with Luke, Leia and Han, we are left wanting to know more about and see more of them. This is why I almost think the narrative about how the characters got to where they were by the time of the Sequel Trilogy sounds, from the snippets we get in the films and putting the spinoff material aside, more interesting than the story of the new characters in some respects.
4. This might be a bit unfair, but is there a slight issue in Return of the Jedi having an overly triumphant ending? Don't get me wrong, I love Return of the Jedi, but the screenwriters only gave it such a happy ending at George Lucas's insistence, and he probably wanted it because a film which left the audience happy would sell more toys to kids. That's probably why Han didn't die on Endor, and why Luke didn't have either of the touted endings he might have had: either falling to the Dark Side and replacing Vader, or "walking off into the sunset" at the end, having been utterly emotionally drained by his experiences. An ending more on these lines might have arguably set up more for Sequel Episodes, but I suppose we can't really blame it for not setting up sequels that even George Lucas wasn't thinking seriously about making until the 2010s (apparently he did consider making at least Episode VII himself before selling the rights to Disney. Google it if you want to know more).
The last thing I wanted to discuss was Luke's ending in The Last Jedi. He stops looking to the horizon and focuses on the here and now: if he uses his great knowledge of the Force, he can save the Resistance, maintain hope in the galaxy and start a new legend to inspire it, while also intimidating the First Order and leaving his fallen nephew with something to think about. He couldn't undo the effects of his failure, but he could act to attempt to help build something new. Now that he's one with the Force, he just needs to make sure to pass this on to Rey in Episode IX...
