Docker can't escape all the blame here - its layer caching mechanism is IMHO flawed. It's fine to say that a packaging system should offer reproducibility but Docker's layer caching design assumes that every RUN command produces reproducible results.

You could of course blame users for not making sure that all the commands they use in their Dockerfiles are actually reproducible but many/most examples even in the official documention are clearly not reproducible.

Therefore you end up with what is in my opinion a semi-broken system - building images seems to be reproducible (and fast) until you lose your layer cache or you spin up a new CI build agent or a new dev joins the team and tries to build the same image.

Not that I can think of an clean and performant solution to this problem.