But Android Auto isn't required to be able to do all of that.
You're saying Android Auto, especially in rentals, is essential for music and navigation, and that you don't know what you'd do without it. I'm saying, Android Auto isn't essential - the phone that you brought with you on your trip can literally do all of the same things. Heck, Android Auto is basically more akin to a mirrored screen, because it's your phone doing all of the work anyway.
It might not be on a screen that's built in to the dashboard, sure, but you've got all of your "essentials" in your pocket no matter the car nor the car's amenities. Find the most optimal spot to set your phone, plug it in via audio cable or bluetooth audio, et voila.
That's the problem though. There is usually no good place for a phone. And the phone holders with suction cups are never that great IME.
But you're kind of right. If we had a phone holder in the middle of the dash we wouldn't need AndroidAuto, it's just mirroring the screen.