How Did He Screw Up Luke So Much?

Is he that responsible?

I think the story arc for the trilogy was already somewhat planned ahead of him writing the script.

https://www.quora.com/Why-do-fans-criticize-Rian-Johnson-for-the-portrayal-of-Luke-Skywalker-in-The-Last-Jedi-when-it-was-J-J-Abrams-that-placed-Luke-on-Ahch-To/answer/Dan-Holliday

Johnson did choose to have Luke be a melancholy, negative douche. He chose to ignore Abrams tone. He chose to pretend that the Knights of Ren didn’t exist. He chose to use a space ship chase. He chose to do Planet Vegas. He chose to include a bunch of worthless side characters and stories. That’s on him.

More to the point, Rian Johnson chose to ignore fan pleas, fans who’ve waited decades. He thought he did right by them. He tried. He really put a lot of work and creativity into it. But entertainment is also religion. You make sure not to fuck with god. God is your audience and they pay you their hard earned money for a few hours of escape. Johnson tried and failed. But Johnson was hired by someone who knew who he was and should’ve done her job in getting an outline in place and then watching dailies, making sure he colored inside the lines.

Oh and she has done that. For years. Kennedy is known for her unique ability to show up on a production and get it back on track. Remember that time she fired Lord & Miller after micro managing them for weeks. Yes, that blew up in her face (after TLJ was released). Thing is, they made the film they were hired to write and produce. Johnson was writer and director. Kennedy and Bergman produced. They should’ve handed Johnson the outline and then kept him in line.