I don't have a high-end luxury car, I've only used Android Auto / Apple CarPlay through the car's microphone system.

Even if we assume a sophisticated system that can triangulate your voice, trying to talk to the car while driving, and having other passengers talking seems like a recipe for distraction.

Perhaps! I was imagining that it would work at least as well as a HomePod, which can pick up very quiet talking even when music is playing. Since the car knows where your head is located, I assumed that it would perform even better. I don't have a problem talking while there are others in the car — I often have kids in the car and use an AirPod to ask Siri to send text messages. I find it to be less distracting than reaching for knobs (and I've driven knobby cars since the 90s, so am well-practiced at that). I find steering-wheel controls to be the best, but anything that makes me reach into the center stack is less preferable (compared to voice interface) for me.