Yeah but if I had the option of Docker or something nix based, why would I not choose Docker? Particularly as deploying to most Clouds is pretty easy if an app in already in a Docker Container.
This is a good starting point:
Also, nix/guix are somewhat lower-overhead ways to build a system for local development than containers.
So Guix gives you reproducibility, provenance tracking, and hackability, but you can still "speak Docker".