I see your point for technical users, what I'm imagining is something where I install NixOS, and then download LibreOffice via a GUI, as is done on Windows/Mac/

I see your point for technical users, what I'm imagining is something where I install NixOS, and then download LibreOffice via a GUI, as is done on Windows/Mac/Most Linux tbh I don't think an LLM is required here; for a very significant subset of nixpkgs I think updating the configuration.nix is a deterministic process.