The main problem is that the car industry didn't want to spend the money to safety-certify new microcontroller designs - by law/regulations, that's a requirement for anything that's safety critical.
It's the things like power management ICs, that have to deal with much larger currents and voltages, that are problematic, and you can't respin those on smaller node, and that's before you go for automotive grade tolerances.
That new MCU with new safety certification (and there's a lot of those going on, even a layman like me can see a push for equivalent of Integrated Modular Avionic in automotive) is going nowhere if it can't get power.