Why is dom0 not minimized and includes unnecessary stuff?
I think the direct cause is that some packages rely on those “unnecessary stuff”. Try to remove the package you dislike and see if something really depends on it.
How to improve that?
I’ll be grateful if you would like to take efforts to identify and remove the unnecessary packages. However keeping the minimal required packages list is a maintenance burden.
And for hardware-specific packages I do not think it’s easy to make them uninstalled by default and then install them on your demand, as it’s not easy to keep the linux kernel ( which is quite bloated with all those firmware and modules that may not be used by your hardware ) light-weighted and contain only those code that you actually use.
And I have to point out that installing additional software in dom0 does not increase the attack surface ( make it easier for random attackers on the internet to hack you ): they only mean an increase on the code that you have to trust. That’s why dom0 can use an EOL fedora release and people do not need to worry. Those random packages are not security critical. As long as they do not contain code to specifically breach Xen and send telemetry home, you are safe.
How can one use a different basis for dom0? (and why isn’t e.g. Debian the default one or an option)