I think you’re trying to have your cake and eat it. Johnson is telling us that within the confines of the Star Wars universe legends have value, but aren’t real. He tries to bring Star Wars into the real world by having Luke doubt the value and reality of his own legend. He then has Luke return in a manner, which enforces his point of view that Luke cannot really be the legend that faces down the FO with his lasersword, but can perform an illusion to make others believe in the legend of Luke Skywalker. Luke rather than being a space wizard becomes a wizard of Oz, a master of smoke and mirrors. The myth is slowly absorbed by reality. It’s an interesting point of view, but on my view clashes with the concepts of the modern myth as set out by Lucas.
That is your interpretation of The Last Jedi, but it is not one I remotely share.