I’m really just spitballing here, but I think maybe the problem people have with Luke’s actions in TLJ is that there has been this Superman-like mistique set up around him by our culture. People assumed (or inferred), because Return of the Jedi ended on a high note for him, that he essentially could or would become the ST’s Qui-Gon Jinn or Ben Kenobi.

It is because TLJ turned around and said “Nope. Actually, he’s had a severe crisis of faith. Whatever you wanted him to do, he’s having none of it.” And so it’s as if Superman is suddenly not for truth and justice (and the “American way”). He’s not what we expected. He’s Bizzaro-Luke.

Humanizing him in this way cuts people deep, I think, because of how we as a culture built him up as a sort of superhero in the 80’s. Whether or not someone read the EU novels.