Ratings are totally absent from the iOS 10 Music app, with no option to turn them on. Currently, on iOS 9, you can view a rating or rate a track by tapping its album artwork while it’s playing, but only for tracks in your library; you can’t apply star ratings to Apple Music tracks. Nothing happens in iOS 10 when you tap the artwork. When you tap the … for a playing track, you see a menu which offers Love and Dislike options, but no star ratings.
I hope to see star ratings return to iOS. I make extensive use of them in a few smart playlists and the new heart-based rating system doesn’t offer enough granularity for my needs.