CMake today is autotools yesterday: too buggy, too unreliable, fragile, slow. Bazel is properly made build system.

Basically, CM does not guarantee correct incremental builds, Bazel does (I had to kill CM cache thousands of times to make sure everything is rebuilt correctly after changes in CMake definitions). CMake is incompatible with effective distributed building (you have to use cpp and distcc), Bazel is designed with distributed in mind. CMake is incompatible with effective caching (you have to use suboptimal ccache), Bazel has proper caching based on input checksums. CMake macros are pain, Bazel macros and custom rules are nice. And so on.