Any smartphone could be plugged in via a USB-like cable which transfers I/O, audio and power. The car's up/down/left/right "radio" buttons would then control like/dislike/next/previous for Pandora-like apps running on the phone. Throw in another 2 buttons or so for other functions. There would be an open "key-mapping" standard which would be implemented in the OSes which music apps could tap into. There would be a standard set of programmable-per-app buttons (not unlike video game controllers)

Voice is unusable when music is playing and touchscreens are too dangerous. Mobile and digital entertainment technologies move so fast, yet I only change my car twice in 3 decades or so - I don't want to be constrained by what technology was available when I bought it.