How is CarPlay controlled?

[mw77]

Plan

Premium

Country

USA

Device

(iPhone 11)

My Question or Issue

Wondering who is responsible for the UI of the Spotify CarPlay design? Is it up to Spotify, the radio manufacturer, another party or a combo of some of these?

I'm using a JVC head unit in my car and am disappointed by the lack general features in spotify via CarPlay. For example the simple "+" feature when listening to suggested music is far too limited and Spotify needs to add some sort of "thumbs up" "thumbs down" functionality. Just wondering what is the best route to send suggestions and follow future development of CarPlay functionality.