I love Mark Hamill and definitely have problems with Last Jedi but he's a bit delusional when it comes to Luke.
Luke was never the most optimistic character in the galaxy nor was he all good. He brought balance to the Force. He was wearing all black in Return of the Jedi and had a bit of a cocky attitude. He was half light, half dark and that's what brought balance.
I think it makes perfect sense what happened to his character and is a throwback to what also happened with Obi and Yoda.
I think in Hamill's mind, Luke should come back, save the day and the movie be all about him. While the kid inside me would love that, that's not realistic when you are trying to tell a new story and introduce new characters. Luke doing something that has never been done before and is the film put it, died with peace and purpose is a strong ending to the character.
While I wish they would have saved it until the 3rd movie, I ultimately didn't have a problem with what they did outside of a few minor complaints.