1. read the GNU Make manual 2. Write a tiny build system with Make or use any of the precanned ones. I use this: https://github.com/dkogan/mrbuild/ but there are many others
In any case, learning how to actually use Make is a prerequisite to having an opinion here.
4. Follow its advice until you hit the end of where it is useful. (i.e., you can no longer count the number of $ escapes in your own code).
If you truly need a lot of complexity, you can end up with unreadable Makefiles, as you say. Most projects don't need a lot of build logic, though. I have lots of projects using mrbuild, and their builds are clear and easily maintainable. If you truly need a lot more, then Make might not be the best choice. And you can do much better than cmake