I disagree. I don't use Nix, but I've been in situations before where an upgrade either couldn't complete, or catastrophically broke something. Those situations are horrible and can take hours or days to resolve.

Having the option to say "fuck it" and just reinstall everything, without worrying about manually installing exact software versions and reconfiguring everything sounds amazing.

I think the important thing that did not come across very well is that "wipe and reinstall" with nix is so incredibly painless that doing it is even an option. The same would be very very painful with other distributions. A clean reinstall of your whole system with nixos takes maybe 30 minutes. Compare with the average "my Ubuntu upgrade failed" debugging session...