my tendency is to reject such tools because there are so many tools like this and everyone uses a different one
There are only a few tools like CMake, actually. It's very different from autotool, scons, etc. It's not a build tool, it's a build files generator.
You'd like to have a SFML project that you can open in your favorite IDE. That's fine. But how do I generate and maintain such build files? How do I ensure that it has the exact same behaviour as the build files for all other platforms that people use? It would be crazy to maintain a build file for every supported OS/compiler (there would be ~10 of them). That's where CMake helps: from a single definition, it can generate makefiles or projects for whatever tool/IDE you like. And the best thing is that you only need to run it once: after that, if SFML build files are updated, your project/makefile will automatically apply the changes to itself.
So in fact CMake makes it possible for you to work with your favorite tools, it doesn't replace them. Without it, I would have to "
reject some build tools because there are so many and everybody uses a different one"
Don't misunderstand its purpose.