CMake is not a package manager or package repository, though. CMake can discover libraries and it can build your code, but that assumes you've already fetched a dependency somehow. Sure, you can use system package managers, but these are different on every platform.

I've been writing a simple video game in C++ recently, using CMake to build. I wrote a little bit of code that fetches the few libraries I need in order to have a complete/deterministic build process that works on linux/windows/mac. It lets me change versions (by specifying a new url to a source tarball). Versioned dependency management is so typical and convenient in many other languages and is such a pain in the butt with C++ because CMake is this thing that's sort of good enough. But my CMake experience doesn't compare well at all with maven, pip, gem, cargo, or even npm.