If the only way you approach the argument that Luke has been characterized improperly is by saying that the audience is merely blinded by their emotion, insofar as to say they should be ashamed of being impassioned by their connection to the films, the conversation doesn’t last much longer afterwards.
I’m not saying the audience is blinded by their emotion, simply that they choose instead to not move past that reaction to the decision having been made at all. This depiction of their fictional hero bothers them very, very much, to the point where their deconstruction of why it doesn’t work goes very, very deep in many ways, some intentional, some unintentional.
It honestly doesn’t need to be justified any farther beyond “I don’t like it, and I don’t like how it happened, I don’t like that it happened, and it bothers me that my fictional hero of choice was written to behave that way.” That’s honest, and true, and there’s not really any counter-argument to it. It’s rooted precisely in how you feel, and you don’t need to justify it beyond that, and you don’t need to respond to people who unfairly ask you to justify it beyond that point, really. If you simply don’t like that Luke Skywalker was put in that position and did the things he did, there’s nothing more anyone can say, honestly. You didn’t like it. There’s not really a way to “fix” that or talk you out of it. I can share why it worked for me, though. But that’s not being done as a means to convince you of your wrongness or anything like that. It’s just part of the conversation, and a desire to be understood.
I enjoyed it a lot. It’s likely I’m inclined to enjoy it, not just because I recognize and empathize with depictions of depression and struggle, and not just because I enjoy watching people figure themselves out and triumph accordingly, but because I don’t really hold these characters as sacred? Star Wars is for messing with. While this whole place was borne out of a notion that disagrees strongly, it’s also a place that has come to nurture and promote that specific notion. Star Wars is for messing with. It’s malleable. You can do things with it, and many of the best things that have happened with the property have happened precisely because people wanted to mess with it, to make the characters do things they otherwise wouldn’t do, and then see how they react, how they grow (or don’t) and what that might say about US, here in the present.
The idea that Luke Skywalker became a depressive old hermit who checked out for a decade because he was so ashamed of himself and angry at losing touch with what made him “a legend” in the first place? That’s not blasphemy to me. That’s interesting. And the way it was done was not just sad, but charming, too. To a lesser extent, a similar thing was done with Thor in Endgame. And to a lesser extent, some of his fans reacted much the same as Luke’s fans have reacted: The decision to do it was, in and of itself, unforgiveable, and so anything built upon that (to them) broken foundation isn’t worth giving over to. All they see is the humiliation and the “disrespect” to such a strong character. They see that as a punitive act against their hero, and they basically just… stop there.
I don’t think it’s disrespectful at its core to do things like that to beloved characters. They’re not people, they’re ideas being explored. And I think if you nail the execution, you’ve almost always managed to make that character even BETTER than they were before. I feel like the Luke Skywalker I saw in The Last Jedi was maybe the best he’s ever been, and it’s certainly the best performance Hamill’s ever given, and it seems messed up to me that he wasn’t seriously considered for a best supporting actor Oscar. But he couldn’t have been that great, I don’t think, if Luke hadn’t been put through those trials and tribulations.