I do use Ninja when I use CMake, but honestly that mostly comes down to the fact that the Makefiles generated by CMake are horrifically slow. I don't particularly love CMake, I only use it because the C++ ecosystem really has nothing better to offer. (And there's no chance I'm going to redistribute a project that can't build with the Makefile generator, at least unless and until Ninja is default.)

Anyway, the Google C++ style guide has nothing to do with why C++ modules aren't and won't be used at Google, it's because as-implemented modules are not an obvious win. They can theoretically improve performance, but they can and do also make some cases worse than before.

I don't think most organizations will adopt modules at this rate. I suspect the early adopters will wind up being the only adopters for this one.