I get it. I recently switched to NixOS from Arch and I absolutely love it. I would routinely go buck wild with Arch and eventually my system would just be populated with garbage or half assed things that I never bothered to fix. With Nix I don't have that choice. If I fuck around with the config well then it's not rebuilding and I need to actually fix it. It prevents me from breaking my system. If I do somehow many to break something then I can instantly roll back from the grub OR just retrieve a backup copy of my config which I keep on my server backup and my private git instance. Just have to git clone it.
So I was once one of those anti-immutable people but now I get it and i love it.