To be honest I don't know what to say, you can use nix in many ways, and you don't even require to know the language.

The easiest entry-point is to just use it like a package manager, you install nix (which is just a command...) and then you have available the whole set of packages which are searchable from here: https://search.nixos.org/packages

nix-shell is just to download&add programs temporary to your PATH.

I don't feel that this is harder than something like "sudo apt install -y xxxxx" but for sure more robust and portable, and doesn't require sudo.

If at some point you want to learn the language in order to create configurations or packaging software, it may require to check a lot more documentation and examples, but for this I think it's pretty straightforward and is not harder than any other package manager like aptitude, homebrew or pacman.