After 15 years on iTunes, and much devotion towards keeping a clean library of music that I ripped or purchased, Apple Music ruined it for me.
Especially in iOS, where it did not understand the concept of not having a constant internet connection, like it was implemented by some 21 year-old newb that had never made any production code in their life. This made Apple Music completely useless for my primary use case; driving along the coast on Highway 1.
And that's not even getting to their poor aping of Spotify's UI, without even understanding what makes Spotify work, and mucking up everything in the process. And the atrociously non-functional and ugly flat UI with no communication about what you can tap and what is not tappable.
Never again will Apple Music get any of my money, and never again will I trust Apple with my music. It was a major turning point in everything I do with them; I've always had easy escape routes for all my data to leave the Apple ecosystem, but it was the first time I had to use one in practice.
I've switched to Spotify, abandoning all my investment of time and money into my music library. I don't have time to invest in that anymore.
Building an app on top of anything Apple Music is folly, you'll always be fighting against their changes in formats, and you can be locked out at any moment.