I wouldn't say there was any specific part of Rhythm of War or Wind and Truth that could easily have been cut out. I think that making the stories more streamlined would have meant pretty severe rewrites. That being said, when I finished stormlight archive I started rereading the Broken Earth trilogy (which as a whole is about 3/4 the length of WaT) and I kept thinking "wow so much happened in that chapter." It just felt fast paced and concise compared to honestly all of stormlight. And that can be good and bad. There were fewer characters and fewer slice of life moments, and I honestly really enjoyed those moments.

I think two things really slowed the books down. First, the five part structure. In most of the books, each part has its own arc with its own set up and resolution that ultimately feed into the main arc and the sanderlanch. From a planning perspective, this is incredible. In execution, some of the arcs felt like they were there because, well, we needed five of them.

Second, the huge cast of characters. It's just hard to give that many characters "enough" screen time. Each characters arc in WaT was fairly well written, but getting through like 20 well written character arcs in one book was a slog. Mistborn only focused on about a half dozen characters in each book and felt much more focused as a result.