Most package manager formats are simple text files as well.
Also, docker doesn’t solve the DLL hell problem, just pushes it out of sight. The nix package manager is something that actually solves it and it should be promoted and leave docker to things it is good at - containerization.
That! It is codified. If people had their main machine codified, Docker would maybe be less of a benefit. And I'm sure a lot of people here have that. But a lot of my colleagues don't. So, I give them a Docker image... instead of explaining the same Java developer for the umptied time how to make a virtual environment for my Python program.