Many comments here make the point that configuration languages often pretend to be code and they do so badly. The conclusion is then that we should simply use code instead.

I'd like to propose that there is no fundamental distinction between code and configuration languages. The distinction is actually between total and non-total (Turing-complete) languages. Configuration languages are just programming languages of varying complexity. Some of them are total (i.e. non-Turing-complete) and that's a good thing.