If you've spent time with Nix, I assume you heard about Guix at some stage. And if you've heard about Guix and still make the above comment, I assume you have some reason(s) to think the Scheme programming language doesn't solve some/all those problems you mention.
Nonetheless, in case those assumptions are off - GNU Guix exists, and is written in and extended in (Guile) Scheme. Guile is general purpose, has the excellent Andy Wingo powering a lot of improvements to the language the last years, and some people are very fond of it. Perhaps you'd be interested in investigating, if Nix's DSL wasn't to your liking.
Nonetheless, in case those assumptions are off - GNU Guix exists, and is written in and extended in (Guile) Scheme. Guile is general purpose, has the excellent Andy Wingo powering a lot of improvements to the language the last years, and some people are very fond of it. Perhaps you'd be interested in investigating, if Nix's DSL wasn't to your liking.