They did not want to rehash Star Wars, or Luke would have been physically on Crait and would have let Kylo strike him down so Leia and the rebels could escape the way Obi Wan let Vader cut him down on the death star.
It was a bit too late for that if they were worried about rehashing. The first half of the throne room scene was borderline plagiarism already, and the battle of Crait was very Hothlike. I have heard people point out the Luke-Yoda and the island-Dagobah parallels before. TLJ is quite derivative, and the most original portions of the movie (Canto Bight, the mutiny subplot) are generally considered to be the worst parts of the movie.
In the version I wrote above, Luke doesn’t let himself get cut down. He’s trying to stay in the fight as long as possible to protect his allies and give them time to escape. And the whole time, he’s trying to reach out to Ben, as Luke would.
They sort of did it but with Luke as a force projection instead so Rian could say it was original. And so Broom boy got his legend.
That’s the part that doesn’t make sense, though. How would Broom Boy, or anyone else in the galaxy outside of the First Order military or the handful of people aboard the Falcon, even know about what Luke did? How would the legend spread?