It would be better than Windows for sure. You’ve got A/B updates, verified boot, selinux, properly sandboxed apps and a whole range of other isolation techniques.
For something truly mission critical, I’d expect something more bespoke with smaller complexity surface. Otherwise Android is actually not a bad choice.
Any sort of Immutable OS would be better for critical systems like this. The ability to literally just rollback the entire state of the system to before the update would have gotten things back online as fast as a reboot...
Something like Android Lollipop from 2014 supports all the latest techniques. It's likely there's no security issues left on Lollipop by now.
A lot of the new forced updates on Android is to prevent people some apps from being used to spy on other apps, stealing passwords, notification backdoor etc, but you don't need that if it's just a car radio.
For something truly mission critical, I’d expect something more bespoke with smaller complexity surface. Otherwise Android is actually not a bad choice.