I've harped on it enough over the years that I won't go into the whole rundown again, but even if George had actually started at the beginning, it was never supposed to be trilogies -- just an ongoing episodic adventure serial. By locking themselves into the "trilogy model that George established", without understanding the why of it or why it didn't work as executed, they didn't just put the cart before the horse -- that's a whole damn convoy and the horse can't go anywhere.
My biggest frustration, as a Star Wars fan from just about day one, has been all the threads and ideas and possibilities set up in Star Wars and Empire... that then either never went anywhere, didn't get anywhere near enough screen time for what they ended up being, got contradicted or retconned out of existence, or just left hanging totally ignored in favor of new ideas that had only vague associations with the story around them.
The Force being strong in the Skywalker family is let down hard when we find out it's been that way... since Luke's dad because magic. Shmi doesn't seem particularly strong with the Force, and we heard not one iota about her antecedents. There are ways to handle that. Luke's conversation with Leia on Endor chould have gone, "The Force has been strong in my family only recently, but unusually strong." Or else make the Skywalker family a thing going back to the Old Republic. There's stuff about these noble houses and high families in the ancillary material that never gets touched on in the films that is fertile ground for delving into the GFFA's haves and have-nots and how some used their position wisely and well while others did not, the rise and fall of great dynasties. The later Arthur legend is exactly what Luke's story was -- the humble farmboy who turns out to be a long-lost prince. I would have been much more interested in how this once-great family fell from grace, and Luke's struggle to make things right again.
Rian's take that the Force can be in anyone is right out of the original material around the time of the first film. Anyone could become a Jedi, if they had the patience, the self-awareness, and were able to stick with it. Some were just better/more natural talents at it than others. I wish it had stayed that way. Sure, we can still have midi-chlorians and whills, but let that be peripheral. It still takes training, though. I have never been okay with Broom Boy at the end of TLJ. My preferred take on that would've been, after the story group breaks up, he looks at his broom, reaches out his hand toward it and concentrates and... nothing happens. A sound from one of the other kids outside distracts him, he turns his head, the broom handle tilts toward him about an inch... and he drops his hand and just walks over and picks it up without noticing.
Kylo needed time to discover what writers confronted about Vader back in the '90s. There's no way to atone enough for what he's done. Two ways to go with that. One, he becomes about the most Jedi Jedi who ever Jedi'ed -- dedicates the whole rest of his life to serving those he harmed... Or else state publicly to the mob screaming for his head on a pike that his death won't make them whole, but if that's what they demand then so be it, and then after he's been executed, everyone walks away realizing he was right and they still hurt and now also feel guilty.
The stuff between Obi-Wan and Yoda on Dagobah. About Obi-Wan also being full of anger and recklessness when he was younger. We didn't really get to see any of him coming into his own as a Jedi. TPM tried... but didn't have enough screen-time to cover years -- and itself clashed with the OT with Qui-Gon and Obi-Wan going to their sabers before any attempt to de-escalate. Which isn't so much Obi-Wan being angry and reckless as it is him following his mentor's example.
Never mind Luke's sister getting dropped and mashed up with Leia and the thirty frikkin' years between episodes VI and VII with no help to the audience as to what has happened in there, beyond Luke having disappeared at some point prior to the film and Han and Leia breaking up. Because of the internalized structure of storytelling, what we are presented with in the beginning is the "old normal" -- a quo that has been status for some time. The writers even fell victim to this thinking. Like when Poe tells Lor, regarding the map fragment, that "this will begin to put things right". Implying they have been not right for some time. One has to delve into ancillary material to discover that everything was fine for a quarter-century and only went to **** within the last five years. Luke Skywalker disappearing is a thing that happened six months to a couple years prior, around the same time that Han and Leia had a hard time being around each other. Like that's the cliffhanger where the last episode left us, except it didn't.
So yeah. A lot of good ideas and threads that didn't get treated right because Trilogies™. Ugh.