I think this attempt at clarification is just proving xvector’s point.
It's not an attempt at clarification. It's best if you start with the problem you're trying to solve, then work backwards towards a solution.
"Nix" isn't really a thing, no more than "Linux" is. It's a collection of tools and languages and frameworks people use to solve various very different problems.
(Also Nix and Nix-flakes are two different things, like Javascript and React.)