My problem with Luke was simply because he was too out of character. Lucas had written Luke as an idealistic character who wouldn’t give up in the face of adversity. So much so that he was the only one who believed in his father even after the horrible transgressions he committed. So why was that just thrown out the window? Why would he give up so easily? Why wouldn’t he try to talk to Ben before trying to assassinate him? I’d understand if it was shown that Luke made a genuine effort to reach Ben beforehand but we see so little of their relationship that it just make feel little sympathy for either character. If the movie focused on the main plot instead of shoehorning a nonsensical side plot it would’ve been much better.

I disagree that Luke hadn’t mastered his emotions. While it’s true he was prone to emotional outbursts Return of the Jedi showed how his character came full circle. Unlike his father he didn’t succumb to the influence of the devil and threw his sword away disproving Yoda’s assertion that he would turn to the dark side. A man who was able to bring hope to the galaxy and defeat the devil isn’t someone who would regress after that. After all, temptation only works if one can’t master their emotions. Luke is the kind of person who’d be on the frontlines not living as a hermit. On a side note, Yoda went into exile out of necessity as the whole Empire was gunning for his head. Something Luke didn’t have to do.

Also, while Rey was shown to be a flawed character we still have no understanding of her backstory. Since Force Awakens I was curious about how she had such acumen with the Force. The movie had the chance to put the medicholrians in proper context. But there is no payoff, Rey is proficient with the Force cause reasons. Then the movie conveys that anyone can become a Jedi which spits in the face of the established lore.

Finally, given the proper context of that scene it’s a strong indication that Luke was dead.