Yeah, Trevorrow’s initial script for TROS was written more than a year before the release of TLJ, and the same applies to TLJ as well. Watching the first two movies and then reading Trevorrow’s first draft, there’s a clear through-line in the entire trilogy. It’s just that Carrie Fisher’s death threw a spanner in the works.

Yes, there is a through-line, but Carrie Fisher’s death is irrelevant. Leia’s role in the trilogy has always been fairly minor, and her role in DotF could have easily been rewritten around the footage they had. Lucasfilm clearly had a problem with the script itself. I’m inclined to believe it’s the way it handled Kylo.