Of course, the software that goes onto a NixOS installation is the same as on most other Linux distros so it's not any different in that regard. What I was trying to say is the config management aspect - especially when used with an ephemeral root FS - provides an entirely different way of managing your computer that's not really possible to replicate anywhere else (except Guix as I've mentioned).
Not that that makes it objectively better or worse. The config shtick of NixOS can also be really annoying to someone who just wants to install stuff and move on. It comes down to personal preference.
Personally I prefer the approach that the BSDs took: your OS has a "base" that is designed and integrated as a whole, provides basic services (SSH, httpd, mail, etc) plus a spartan GUI and all the tools to support its own development. Everything else is in ports/packages, which theoretically can be erased all at once with no loss in core functionality. It's conceptually simple and works OK in practice.
Notably, macOS (a BSD in my book) took the next logical step and completely sealed the base OS, all the way via logical volume management, verified boot chain, SEP (aka TPM), etc.
I agree that NixOS solves configuration management in a much more elegant way, but that elegance carries a heavy cost: it requires domain knowledge to comprehend. Personally I just keep /etc in git, and use judo to propagate changes. <https://github.com/rollcat/judo>
Not that that makes it objectively better or worse. The config shtick of NixOS can also be really annoying to someone who just wants to install stuff and move on. It comes down to personal preference.