The flip side is that the world still hasn’t settle on a language-neutral build tool that works for all languages. Therefore we resort to running arbitrary commands to invoke language-specific package managers. In an alternate timeline where everyone uses Nix or Bazel or some such, docker build would be laughed out of the window.

That's not going to work if both parties get different hashes when they build the image, which won't happen as long as file modification timestamps (and other such hazards) are part of what gets hashed.

Personally I love using mkosi and while it has all the composability and deployment options I'd care for, its clear not everyone wants to build starting only with a blank set of OS templates.

I wish we had standardized on something other than shell commands, though. Puppet or terraform or something more declarative would have been such a better alternative to “everyone cargo cults ‘RUN apt-get upgrade’ onto the top of their dockerfiles”.

Like, the layer/stage/caching behavior is fine. I just wish the actual execution parts had been standardized using something at a higher level of abstraction than shell.

But as long as people want to use scripting languages (like php, python etc) i guess docker is the neccessary evil.