Quite honestly, I almost chose NixOS over Debian a few years for that reason, but I prefer the community support of Debian. Of course, that could change, but right now, I’m not in a big distro-hopping mood nor am I sufficiently unhappy with Debian. On a side note, it kind of bothered me that you couldn’t use Nix to configure e.g the layout of your XFCE desktop. If I ever transition, maybe I’ll put in some time one summer to make that all work.