We just invested a good amount of time restructuring our docs for Diátaxis. It was helpful, but I wouldn't take it as gospel. The important thing to remember is that each piece of content should be one of the four types.
If you're embarking upon a refactoring / rewriting journey for your docs, the only advice I'd share is to actually read the website beginning to end before starting. Especially this page: https://diataxis.fr/complex-hierarchies/. The guide is (unsurprisingly) very well written, and it's easy to internalize the concepts because they're repeated often.