Luke’s story in ROTJ is not one of becoming successful in spite of his flaws. It’s overcoming those flaws, losing self doubt, and insecurity that make him successful, that make him a Jedi.
And people don’t just overcome things once and then they’re never a problem again, either. If a story has to continue, then drama must ensue. And Luke is a focal point of that drama. Nobody becomes a perfect person at age 30, no matter how fantastical the story is. There’s still a lot of learning and overcoming to be done, backsliding and correcting that has to be accounted for. Our heroes are still people, and people are inherently flawed. That they triumph over their flaws is inspiring. But triumph doesn’t erase everything. But that speaks to your next point:
To me that’s kind of the point of myths, and fantasies, that it isn’t reality. That we do not find out our hero is secretly a drunk, beats up on his loved ones, neglects his or her children, is afraid of hights, suffers from all sorts of compulsions, etc, etc. I don’t get the idea, that making the Star Wars characters more realistic automatically makes them better.
It doesn’t “automatically” make them better, but it does make them more sympathetic and more relatable IF the execution is done well.
Well, I might be more sympathetic, if I didn’t have issues with the execution as well. I feel TLJ failed to really sell Luke’s point of view. That even if you accept Luke letting his fear of a possible outcome get the better of him (despite being a Jedi, who are trained to not let fear control them, and know that the future isn’t set), I don’t see how abandoning everything, and leaving the galaxy at the mercy of two dark siders is in any way a solution to the problem. I feel given our history with the character we deserved a proper setup to his character arc in TLJ. In stead the movie gives us one flashback, where Luke seemingly forgets everything he learned, and then runs from the consequences. This to me makes Luke less relatable, and less sympathetic. In the end Luke needs to be convinced to do the right thing by Yoda, even after he learns of his best friend’s death.