You can use it daily, intimately, without using nixos. Using it for dev environments on macos for example, and servers. Did that for years before I installed nixos on my desktop.

I've been using nix in a Mac for a year now. Recently I got a new Lenovo machine and first thing I did was install nixos, it's actually much better than I was expecting. You do notice that nix is designed around nixos

Maybe it’s everyone else using it on their daily driver that got it wrong?

It’s like doubting Kubernetes because one of the maintainers doesn’t run their desktop in KubeVirt.

What is so interesting about Nix is that it's not one thing. Its not (just) a distro. Its not (just) a package manager. Its not (just) a system manager. Its not (just) a language. Its not (just) a build tool.

It is all those things, but specifically, what you want it to be. Yes, that makes it super confusing, but also powerful.