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>
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>