It's not just about the software but about the hardware architecture of the car. Legacy manufacturers are coming from a situation where they are integrating hardware and software from a lot of different suppliers. This makes upgrading the car a very tedious process and slows down the process of getting suppliers to fix issues and provide new firmware in a timely fashion. It's worse for them because they often want to…
The only formula I know that works is "hire good people and listen to them". From experience, the only way legacy companies can do this is acquire and/or seriously partner with companies that have established a track record in what you need (even if it is only a couple of years, as long as they are _delivering product_).
As software effectiveness/innovation speed/productivity continue to increasingly crush legacy industries, it is extraordinarily frustrating to see how hard it is to make (seemingly simple!) changes.
p.s.: nice to see you Jilles! :-)