It was originally part of Bazel but it is used in other tools, and there are multiple implementations.
But CMake probably will get you a program that compiles cross-platform within an hour or two, even for a novice. Autotools probably won't do that for you.
As such, everything using it is it’s own unique system completely alien and not interoperable with anything else.
And being python seems to lead to people embedding parts of their application as part of the build system, so now that is intertwined also.
I will run a million miles if I ever see a project using SCons, CMake is infinitely nicer, and makes some sense but I agree with further up the thread that it needs a new, saner language that maps over the top (expressions would be a start).
The way the cmake_policy system works isn't bad, but those unfortunately have only limited impact on the language itself.
I recognize that CMake has done a lot to make people’s lives easier, but it has so many design flaws that the entire design seems almost purposefully user-hostile. I know it’s not hostile on purpose, but it sometimes feels that way.