NixOS is definitely more complicated than an OS snapshot - but that's why I like it. That kinda flexibility is what makes Linux great and completely unapproachable, which is why I won't make a bid for Linux domination any time soon. For developers and certain gamers, though, Linux could be a direct upgrade from Windows on their current hardware.
PS, if you are interested in shooting the shit about NixOS, it's actually quite neat. All the time-consuming Linux setup that people loathe can be mostly automated with a config file or two[0]. The package manager (Nix[1]) is pretty badass, and worth checking out if you are on Mac. I much prefer it to Homebrew for dependency management.
I take your point, but "Just Works" on Linux can be a more difficult road than maybe we often care to acknowledge. If you didn't go through the "OMG why won't my laptop suspend properly" years (which maybe still haven't left us...?), then let me tell you UGH, give me a Macbook as my Unix desktop/laptop experience.
I really think it's mostly what you're comfortable/familiar with. Mention NixOS to me and I think interesting, but it actually sounds more complicated than a Time Machine backup on a ZFS NAS to me (although probably much more elegant).