I think the problem is that most people dive right in and go to NixOS which has its quirks as a linux OS (see FHS). The Nix language is great at building and moving source code between computers, really any big collection of binaries. If you don’t do that, try just using the nix-shell command to instantly run a piece of software without installing it. You can write a shell.nix file to hop into and out of an environment with whatever software you need. Once you can write a couple .nix files then move onto NixOS; which after all is just a big collection of binaries.