>> But what _really_ broke my music-listening back was Apple, in their "infinite" wisdom have been rating songs for me they think I'd like in my library (grey stars). As far as I can tell, there is no way for me to distinguish between my stars and the stars Apple adds, which means my playlist of songs that I've rated has now been ruined by Apple's "recommendation."

A quick Google would have explained this for you. They are not 'rating your tracks'. With Apple Music you can 'love' tracks which then show a red heart next to them. The grey stars are shown next to tracks that are the most popular with all Apple Music users. So if you view an album, generally, the singles will have grey star next to them. Really useful when they recommend a new album and you want to listen to the best tracks before digging deeper.