[wkat4242]

Declarative is very different from immutable. They're two separate concepts.

See Apple's implementation where the OS files are protected by signatures and the system won't boot if they're changed. Immutable does mean you can't change it, though I'm some cases you can enable and disable some parts. Nix is declarative and perhaps not immutable. It's advised not to mess with config files but you still can if you wish, it's just a bad idea because it'll be overwritten.

I'm not really against declarative management though I'd consider it something more appropriate for servers where I don't want to change stuff on the fly. On my workstation I don't want to do a complete change time every time I want to modify something. I also don't want to learn the complex syntax so I've never really dived into nix.

I like FreeBSD's compromise of having most configuration in one file but still a traditional system.