I love Nix, all of my machines run NixOS, but I think it's 5-10 years out from widespread adoption. Currently the biggest issues have to do with severely lacking documentation, lack of developer tooling (missing things like LSP), very slow iteration cycles, confusing or impossible to understand errors, and even naming (Nix refers to the language, package manager, cli, community, etc).

That said, right now it's still the best tool I've ever used. Nix is great at a few things: reproducible development environments, reproducible builds, and reproducible systems. I introduced Nix at my last job to do most of these things and it helped onboarding dramatically: Nix-based development environments with automatic activation, Nix-based Docker image builds which reuse the work done for the dev environment, and Nix-Darwin configuration to configure systems with one command. It's incredibly powerful and you're able to use as much or as little as you like. So the amount of "overkill" is variable.

Of course, the problem here is that knowledge of Nix itself is necessary to build and maintain these things. Due to the reasons outlined previously, it is quite an investment. I believe it is worth it given the stability, flexibility, and efficiency Nix can provide.