Windows does have a fallback mode called safe mode and that’s exactly what’s being used to fix this utter mess.
Package management isn’t going to save you from this as it didn’t save the Linux systems affected last time. It didn’t stop Arch Linux from failing to boot after a Grub update either.
Windows also has drive cloning tools, that isn’t unique to Linux.
NixOS isn’t immutable. It’s not an a/b root system and / isn’t read only. Rather it’s what’s known as reproducible. I am not convinced NixOS would make this any easier either given how simple the fix was. Funnily enough though tools exist called ansible and puppet for configuring systems in repeatable ways that apply to both other Linux systems, Windows systems, and even macOS.
There are like one or two valid points in this whole comment and the rest is pretty much falsehoods and misconceptions.
Edit: Forgot to mention tools exist to make Windows immutable as well. So that is an option.