I think it shouldn't be a skill issue because a true professional should learn how to do it :-).
My build configs are systematically shorter than the bad ones.
Also I feel like many people really try to have CMake do everything, and as soon as you add custom functions in CMake, IMO you're doing it wrong. I have seen this pattern many times where people wrap CMake behind a Makefile, presumably because they hate having to run two commands (configure/build) instead of one (make). And then instead of having to deal with a terrible CMakeLists, they have to deal with a terrible CMakeLists and a terrible Makefile.
It's okay for the build instructions to say: "first you build the dependencies (or use a package manager for that), second you run this command to generate the protobuf files, and third you build the project". IMO if a developer cannot run 3 commands instead of one, they have to reflect on their own skills instead of blaming the tools :-).