I’ve tried to improve build times on a large Android project, and failed because basically every dependency gets this wrong and it’s impossible to fix them all.

I’ve tried to improve build times on a large Android project, and failed because basically every dependency gets this wrong and it’s impossible to fix them all. This includes things like Google frameworks that you might expect to be well-written. It’s not well-documented, as you say, and beyond that the tool doesn’t do anything to enforce or encourage correct behavior, or offer you any way to fix incorrect behavior in code you depend on.