In reality you just end up [with] a shitty, nerfed version of a programming language, that [...] users can't understand, because you still have to understand [CMake's] logic to [utilize its magic behavior], oh and [the] documentation is terrible because devs don't bother with the boring stuff. Most of the time [you] end up implementing [workarounds] anyway because [CMake doesn't] actually work properly.
Workflows on the other hand are more conditional and imperative, mapping better to normal programming languages, with the exceptions of transient error handling, long timers and distributing workload. Here, writing a custom DSL would be a much bigger mismatch.
Best for build configuration would be a hybrid, where the declaration of dependencies is done with normal programming language, which at the end calls a build(dep_tree)-function where all the magic happens. With the risk of developers abusing this setup-step and run half the build in their own reinvented imperative flow here instead... trust me, I've seen this happen even in makefiles that run shell commands outside of targets. This is what Scons tries to be, it seems however not to be very popular compared to cmake.
Conan's recent development is promising and it gives you the full power of Python. It can also be used declaratively but with limitations. If I remember correctly, there are discussions in the C++ world about a declarative exchange format for dependencies and build information, but it's in the early stages. It's not trivial because there are also C++ modules now.
Especially gradle.