I wonder how many Nix cheerleaders are aware of OSTree based systems like Silverblue, Kinoite, Bazzite, etc? They provide the same immutability guarantees, but none of the pain and standards-defiance of NixOS.
I think Nix (the package manager) is a much stronger sell than NixOS. You can use Nix to install your apps on top of another immutable OS, whereas otherwise you might go with Flatpaks, containers, AppImages, etc. It's certainly better than adding Homebrew or some other manager like Pacman.
For devs, Nix is nice for people who can't or don't want to use containers for any reason (or want to use both!). I just don't see anyone benefiting from using NixOS except for Nix addicts.
I'm not saying it's okay for Bazzite to have shipped a broken update. That's sloppy.
But you really are being a dumbass here. The solution for your problem is a rollback. That's the whole point of atomic distros: rollback when something breaks using a single command (or just reboot and pick the grub option). Why bother with atomic if you're not going to use one of the killer features?
And in case you didn't know, Flatpaks aren't part of your OS, so you can still do
flatpak updateeven if you don't update Bazzite. There is literally zero cost to doing a rollback, and that's by design.