I am not complaining about those abstractions being possible, I am complaining about them being necessary for doing basic stuff that every other modern language

I am not complaining about those abstractions being possible, I am complaining about them being necessary for doing basic stuff that every other modern language solves with a builtin dictionary datatype. The more you use those abstractions the worse your error messages will get and the harder it will be to understand what is going on. JSON would at least work consistently and don't randomly redefine the meaning of the language midway through a config file. YAML numerous issues of its own, so I'd avoid that if possible. This isn't a Guix specific problem, the GNU project has tried to make Guile a thing for the last 20 years or so, and it just never looked especially elegant to me in any context and never really gained any real adoption in the wild either. And when it comes to package configuration, it's just an unnecessary issue, we already had Nix, which comes with it's own JSON-like language specifically build for this task and that is much nicer to work with than Scheme, because it's configuration language first, not a general purpose programming language turned into one via macros. Using Scheme instead just doesn't improve the situation in any way in my eyes, it just creates a lot of additional problems.