I still disagree the movie disrespects Luke in any way and felt the movie gives him a conclusive arc.
just like any examples of poor writing,
there are in fact successful ways to write a fallen/washed up Luke storyline, but TLJ fumbled it horribly
he literally left his best friends and sister to die, no matter how much he now hates the concept of a Jedi he wouldn't do that
he'd show up committing to using nothing but his own strength or piloting, cutting himself off from the Force, because helping his sister is more important than anything else
he'd even do it by way of feeble apology for fucking up her son (not true, but in his eyes)
everyone else has to already be dead, partly due to his own failings, in order for him to have nothing left to live for
he even says shit like "the Jedi created Darth Vader" and Rey says "yeah but a Jedi redeemed him too" and either the premise is so wrongheaded to begin with, or the writing is too weak to have him come up with any retort
given his history he also wouldn't even think of attacking his own nephew, he'd sit down with him and say "hey dude I know something or someone is occupying your thoughts, can we work this out, I'll go with you to confront it whatever it is" etc etc
or even flip it around, have
Kylo standing over
Luke with an ignited lightsaber, and Luke's failing was to dismiss him from the Jedi school