Well this is enough to put anyone off Nix. Such a shame because the abstract idea is obviously a good one. But every time Nix/NixOS comes up the story is the same. Terrible UX. Terrible documentation. Is Guix any better?
Ironically, there are lots of blog posts documenting how people worked around the poor documentation, but seemingly few fixes being made in the upstream docs themselves. The excellent Arch Linux Wiki demonstrates that high-quality community-maintained docs are possible.
In reality Nix is a programming language. It is a relatively simple language, but it is also functional and lazily evalated. And while the language is simple, its stdlib (nixpkgs) is actually puts another abstraction layer on top of it which is quite complex.
I do think though that Nix should do the same thing other programming languages do: identify what the nix stdlib is, move it to a separate repo with its own release schedule and ensure that whatever is added to it/removed from it is documented.
This won't help author of this blog, but it would be a great help for anyone who is willing to go through Nix Pills.