Docker on Ubuntu can be improved because Ubuntu is not minimalist at all; it comes with a lot of software by default. This has led some individuals, including myself, to try using Alpine, which is more lightweight, allowing the container to run on a more lightweight operating system that potentially uses fewer resources and reduces costs. If Ubuntu were a little more minimalist, that would be good, but it's not really aiming for that since it intends to be the baseline. Also, Ubuntu moves very fast, possibly faster than other operating systems like Debian, which could demand operational heavy upgrades to major versions every couple of years if there are many applications running.
