One of the limitations of Apple Car Play is, like most Apple implementations, the button that activates siri (the "speak" button) will only activate Apple apps.
On android auto you can press the 'speak' button and say, "play XXX on spotify". Pushing the 'speak' burtton in Apple will only support Apple apps (so no opening waze, google maps, spotify), which pisses me off about apple to no end. Also, there is a significant Android update coming (late summer I believe) that makes the interface more visually appealing and adds some features. You may choose to wait and see if that takes care of your issue.
https://www.cnet.com/roadshow/news/google-android-auto-summer-visual-update-2019/
On android auto you can press the 'speak' button and say, "play XXX on spotify". Pushing the 'speak' burtton in Apple will only support Apple apps (so no opening waze, google maps, spotify), which pisses me off about apple to no end. Also, there is a significant Android update coming (late summer I believe) that makes the interface more visually appealing and adds some features. You may choose to wait and see if that takes care of your issue.
https://www.cnet.com/roadshow/news/google-android-auto-summer-visual-update-2019/