Same here... Switched from iPhone 7 to Google Pixel 2 and Apple Music is being super frustrating to use. I'm used to auto-playing songs when the iPhone connected to my car's stereo, but this doesn't happen with Apple Music on Pixel, while Google Play Music works fine. On top of that, I also have issues while playing: the playback can stop for some reason and can't be resumed from my car's controls, could be continued only by opening the app on the phone itself and tapping play. I also have a strange bug with displaying song info on the car's screen: the info displays nice at first, but only for 2 or 3 songs and than it disappears. I was so frustrated that I even tried to switch from Apple Music to Google Play, but I have a rather large library and none of migration services (like Stamp, Soundiiz) were able to transfer my songs.
I really hope Apple would address those issues.