Docker is the opposite of reproducible. The idea is that you (as a user) have a known tested good image you can re-use it easily without having to worry about r

Docker is the opposite of reproducible. The idea is that you (as a user) have a known tested good image you can re-use it easily without having to worry about reproducibility (which is the responsibility of the other side - whoever is producing the images). If you could reproduce that environment easily and instantly, you wouldn't need Docker since you'd just reproduce it every time.