Nix is not great for casual Linux desktop usage - I tried installing the Atom editor, and cancelled when I saw X11 being downloaded. You might as well run NixOS in a VM.
It's hard to say what caused this without more information, but the flip side is that it demonstrates the power of Nix. Everything required to get Atom working--all the way down to something as basic as the display server--is explicitly declared in the configuration and can be downloaded and installed with one command. So although this wasn't what you intended, Nix was actually doing what it is supposed to do: acquire every necessary component (as per the specification) for your application to work.
This is true, literally, of every package manager that came before Nix and every one that will come after. It's fundamentally what a package manager is and does. This isn't the power of Nix -- it's table stakes.
Isn't generating and installing a dependencies tree one of the most basic tasks of a package manager, at least since apt and similar came about in the late 90s?
This is a feature. Nix is completely isolated from the host system. It manages its own dependency tree. Using libs and other things from the host system would be both brittle and nondeterministic, negating the reason why Nix is so novel in the first place.
Ah, I can understand the concern on OSX (or other Linux distros). Earlier in the chain, you wrote "Linux desktop" -- which, to me, implied using NixOS :).
Wayland and Weston work and there's also non-Weston compositors (window managers) like sway, kwin, gnome and more that actually work decently enough with Xwayland integration for running legacy (X11) apps.
