I think it's more reproducible like a recipe.

Yes, baking doesn't work the same at sea level vs say denver colorado @ 1 mile, but pretty much you can share your recipe with friends and save them lots of time.

Most are not, that's true.

It is possible to get to reproducibility though, by involving lots of checksums. For example you can use the checksum of a base image in your initial FROM line. You can download libraries as source code and install them. You can use package managers with lock files to get to reproducible environments of the language you are using. You can check checksums of other downloaded files. It takes work, but sometimes it is worth it.

That work is hard and the tooling is bad and it only takes one mistake, like forgetting to suppress the mtime of your files.

Docker was good enough, simple enough, and got the job done. It won for good reason, but the next generation should learn from it's mistakes.