You are of course right. It's just that Modules inherently put a lot of responsibility on the build system. Among those, but not limited to: a "module registry" wasn't standardized and is in the hands of the build system.

Systems like ninja needs to know modules, which took time and then a stack further up systems like CMake needed to know modules, which took time. That's my answer to the parent "why are there so few modules projects". Because it took time for the ecosystem to catch up.