I have a long-standing theory that all of the Disney Star Wars movies save The Last Jedi were edited to hell. Rogue One was edited and reshot also, but at least it makes sense.
I also strongly suspect that Finn was going to be the star of TFA and SW was using "racist fans" to cover for pandering to the Chinese.
They talked about it being the smoothest production. I understand TFA's issue was that it shut down when Harrison broke his leg and they were able to step back and look at what they had filmed. See what was working and what wasn't. Did rewrites. How much changed, no idea but I do think ideas like Starkiller being added and the final act significantly changed are possible. While I don't know specifics because it was a conversation before TFA came out, the guy I knew working a ILM was saying he was surprised how much everything was constantly changed in the film.
It's been well documented but JJ's approach was to get everyone's input on what was being done. Where as RJ's was to deliberately shut out anyone else's input. He was Howard Roark, determined to do his film everyone else be damned. Than Ayn Rand shit explains why it displeased so many and also why people defend it.
TLJ was meant to film the month after TFA came out. It got delayed a further month for rewrites. The how and why unknown. The further we get from the film, the worse our memories get but my understanding is that it was most likely a rewrite that added Rose Tico and Admiral Holdo. Both actors were announced at the start of filming.
Originally it was Finn and Poe that went to Canto. RJ had commented he couldn't write the characters to be distinct. The dialogue for each could be interchanged. The characters of Rose and Holdo also featured heavily in reshoots. RJ stating that he hadn't figured out the characters yet because they were so new when they first shot them. So we have to assume most of their scenes were changed a couple of times.
The interesting thing to me is trying to reverse engineer all the changes this made to the film and while not knowing how Poe and Finn going to Canto would have been. It seems almost every change I can directly relate to this is bad. For starters, Poe is an experienced person. So you wouldn't have two retards at Canto. Is shit like Finn and Tico meeting DJ absolutely retarded because it's just fitting changes in that don't work.
Was Mary Poppin's Leia a result? The dumbness of the space chase?
It can even go a step further to the notion that the film was meant to open with a battle on Crait and that was repurposed for the final act. Added the awful opening sequence for Rose's sister to die. It also explains why the whole Crait battle is absolutely retarded. One has to wonder if how many of the dumb things in the films actually stem from a production and story that was just spiralling out of control. There were reports about how RJ would rewrite scenes with no thought to the larger script.