Modus is not really an alternative to Nix as a package manager, but to Nix as a language. It has several advantages, for example, it is non-Turing-complete, so there can not be infinite loops, and its definitions are more concise thanks to its logic programming foundations.
Saying that, I agree that an integration with package managers can be beneficial for reproducibility. This is the area of our current research.
Modus is not really an alternative to Nix as a package manager, but to Nix as a language. It has several advantages, for example, it is non-Turing-complete, so there can not be infinite loops, and its definitions are more concise thanks to its logic programming foundations.
Saying that, I agree that an integration with package managers can be beneficial for reproducibility. This is the area of our current research.