The whole sequel trilogy is inherently flawed. In TFA the First Order makes no sense. It's as if the Nazis who ran away to Brazil somehow amassed a fleet and got revenge on America 30 years later. The difference is Lucas based his politics on real history instead of just making shit up. The original Empire's power makes sense as it's simply the Old Republic with new politics. First Order makes no sense, to say nothing of how much bad science is in JJ's films.
Finn should have been the main character. Unlike Rey who just finds a droid Finn makes an active choice to leave, accepts the consequences and has to deal with them. He is also more heroic in the end facing Kylo and suffers injuries unlike Rey.
Last Jedi needed a few more drafts. (TFA did too but it took fewer risks so weak plot elements do less damage) Tropes such as "bitter old man" are used all the time and are fine to people who haven't read every EU novel (such as myself) BUUUUUUT....
If Finn isn't going to do anything in TROS then let him die heroically in TLJ instead of that stupid crash with Rose Tico . If Luke is gonna die let him raise the X-Wing fly there and go out in a blaze of glory. Have Rey join Kylo for a great cliffhanger. Rogue One is also a very flawed mess of a movie but it ends well and we see Vader kick ass which was enough to make it a fan favorite.
The issue with TROS isn't that it's having to "fix" TLJ. It actually spends very little time doing that. The issue is there is basically no plot. (Things moving on screen aren't a plot) Really all the heros need is the location of the evil planet and they go around finding trinkets to achieve this boring goal. It's like playing Uncharted but JJ holds the controller. So the movie is overstuffed and over long but for no real reason (unlike say Lord of the Rings)
The reason Kylo and Rey sort of work is because they're the only characters who are driving the plot based on their characters' internal desires. Everybody else has material goals (daggers, code breakers, fuel) Again Finn started by making choices internally but then got roped into fetch quests with the rest of them.
To me Disney hasn't made a complete single great SW movie. They've made parts, like the first 40 minutes of TFA and the third act of Rogue One. But it's never all come together, and I think a big issue was lack of planning and just rushing the movies out.