Same story here: complex build scripts in CMake, horrible language but at least it has some form(s) of user-defined abstraction. Tried to look into Meson, bumped into this issue, and decided against it for the same reason.

I kinda get the rationale that no abstraction primitive should drive common patterns into the standard Meson distribution (an approach which has problems too, but at least it makes sense to me).

However, seeing function definitions rejected on the basis of Turing-completeness raised serious doubts about the project at the time, and things haven't changed much on this front apparently[1]

[1]: https://mesonbuild.com/Syntax.html#userdefined-functions-and...