Oh boy.
"Every time I think I'm out, they keep pulling me back in!" Okay here goes.
Unlike others (and unlike doomcock), I'll take the time to provide links in order to source what I say here. Filming of TLJ wrapped up in July of 2016 (check the link below if you don't believe me). Carrie Fisher died 5 months later, in December of that year. How in the world was Rian Johnson going to re-write a film after her death in December, when everything had been shot and finished by July?
https://ew.com/article/2016/07/22/star-wars-episode-8-wraps-filming-rian-johnson/
When Carrie died, they were already well into post-production, and the movie was ready for screening in September of 2017. You can read about that in the article below.
https://www.cheatsheet.com/entertainment/star-wars-last-jedi-wrapped-production-early.html/
And as far as RJ shooting off of his first draft, what if I told you that production of TLJ was delayed because of script re-writes? Yeah, that's right: not only was it not based on a first draft, it was actually postponed due to a *re-wriiten* script. Don't believe me? Just read the article linked below.
https://movieweb.com/star-wars-8-script-rewrites-force-awakens-characters/
How about that unresolved little matter of the First Order vs. the Resistance? Was that not the overarching plot of the sequels? TLJ not only left that in play, but put the Resistance in such a disadvantaged position as to necessitate something dramatic happening in the next movie.
How about the grandson of Anakin/Vader having ascended to the throne of a burgeoning empire?
How about "see ya around, kid" where Luke could now be "more powerful than you can possibly imagine" in his interactions with his nephew?
If you find none of this intriguing, that wouldn't surprise me. People who have disliked the ST from the start (or even just after TLJ) would obviously be less interested in the plot points left unresolved. If you don't like the FO because you think they represent a cheap copy of the Empire, you probably don't care about how the *main plot point* of the ST is going to resolve itself after the middle chapter. And if you don't like Kylo Ren as a character, you probably wouldn't care to know how he handles and resolves the lofty position of power that his grandfather had once sought. And if you don't like that Luke wasn't the main hero of this sequel trilogy, then you probably won't care what he might do as a ghost to patch up what went wrong as a result of failing to keep his nephew on the side of the light.