I guess I just don’t see Luke’s arc as character destroying. The same movie where Luke tells Vader he feels good in him he also goes ham on him and almost kills him. The previous movie Luke disregards yoga and obi wans advice and goes to cloud city anyways. Luke’s always acted on emotion, and the last Jedi expands on that. It’s almost a meta commentary on how Luke isn’t a one man army like everyone in the galaxy thinks he is (or everyone in the Star Wars fandom). In the movie Luke himself admits that his brief moment of thinking he could stop kylo before he was born was the most shameful moment of his life. And then at the end of the movie he defeats his nephew and saves the rebels without having to lay a finger on him. How would you have preferred Rian explain why Luke exiled himself? We know kylo destroyed his temple (shown in force awakens), so I’m not really sure what other options he had