Even from this perspective, it's pretty easy to make things more secure by having less technology. Have the infotainment system just be a blank canvas for Carplay or AA to display on (there does need to be a bit back and fourth, phone needs to send audio to car, car needs to send GPS, speed and state of charge to phone (not strictly necessary, but there are user benefits from the phone having this information). The car itself doesn't need a whole internet-connected general purpose computer attached to it, but doing that is an easy way for the manufacturer to supposedly add value.
Similarly, the LG kerfuffle could be solved by their monitors just being monitors, and not throwing in pointless extras that just broadens their attack surface. Monitors don't need to be general purpose computing devices either. I shouldn't have to worry about general computing problems, like getting infected with malware, outside of computers that obviously are general purpose (i.e. phone, desktop, laptop, and anything else I intentionally set up with foreknowledge of it being general purpose and internet-connected, like a Raspberry Pi).