I can't see any reason they couldn't go together. Fully using nix is a trip off the deep end of the learning curve, but there's nothing preventing a beginner using a predefined nixos configuration so long as they stay inside the guiderails. With a bit of care, it should even be possible to let them enable whole add-in .nix files to do things like "check this box to enable proprietary nvidia drivers" (which includes a predefined module that handles that).

Actually, I think nixos could be a wonderful base for a beginner friendly OS, by limiting the user to very specific configurations which have been well tested. Don't allow the user to shoot themselves in the foot. But if you allow the user to start writing or modifying nix configurations, then all bets are off.

I think it should be pretty easy to pick up for anyone who has experience with any other Linux distro, or even just experience with command line. The docs were clear and current when I got started with it.

having the raw power of nix/nixos hidden behind a normie friendly UI layer has insane potential. It basically eliminates any potential for horrible dependency conflicts and gives users an undo button for all but the deepest (i.e. bootloader / firmware) level changes to their system. nixpkgs is also the most comprehensive and up to date linux package set by a huge distance.

I can see something where nix is used for the immutable base, and then the user installs apps using flatpak or similar. Kinda like how fedora silver blue and other immutable distros work.

Arch has always been 'beginner friendly' according to Arch users, so why can't Nix? /s

But, yeah, Nix can be really nasty to troubleshoot because of the lack of information. The Nix documentation is still PITA, and the much of usual Linux guides (which are everywhere on the internet) won't apply to Nix systems. You have to learn a lot.

If what you want is a simple system with a web browser and some games, this should mostly work, but Fedora Silverblue would provide much more integrated and solid DE for that purpose. Being image-based release-based distro, it does offer pretty decent UX. Nix is rolling release, and everything is scattered just like Arch.

That's the whole point of snowflake OS. You obviously didn't spend any time looking into the project. The idea is to have GUIs that configure the OS like any other distro, and write and build the Nix configs behind the scenes.