Ultimately, this story should be about Luke Skywalker in all his greatness and legendary accomplishments passing the torch to the new generation. As great as your generation is, what the goal should be is for the next generation to surpass you and be even greater. Also that Luke's legacy won't die with him and will carry on with the next.
I think in many ways, Johnson had the right idea, he struggled to execute it. I truly believe with a few rewrites, Last Jedi could've been fantastic.
IMHO when Yoda says, "We are what they grow beyond. That is the true burden of all masters." THat's a brilliant and beautiful line. It sort of sums everything up thematically. What if Luke were to even struggle with the idea of someone even surpassing him? That would be an even better story. Luke having to come to grips with that. I just don't think Johnson fully brought those ideas out. He needed people who would give him serious constructive feedback and really do that. Look just like Lucas had great collaborators with the 1977 film. Not to mention, some of the best story ideas that came out of that film came in the editing room during post production.
If you want a good example of a story that does this the right way, look no further than My Hero Academia, especially the movie Two Heroes. It's weird because Two Heroes feels like a weird response to Last Jedi of sorts. It even addresses the problem of fanboy nostalgia and fans desperate to maintain the status quo who are opposed to change.
