This post is dead-on. I've been trying nix in different forms for years, and it's been incredibly painful. The way the folks who use it normally talk about it is so different from real-life use by non-experts it feels like gaslighting. I only felt vindicated when reading https://ianthehenry.com/posts/how-to-learn-nix/ -- it's not me it's them.
Maybe one day it'll get good enough to be usable. Right now it's a long, long fight to get productive in any non-trivial (e.g., explicitly supported and documented) configuration.
I've been messing with GUIX, just because the configuration language is much less confusing to learn and understand.
You might as well try Spack, it's Python + a dsl to customize builds in a single line. Guix package descriptions look very daunting to me.