Allen Pike has a good summary of how limited the media player framework is on iOS, especially for developers who want to create apps that integrate with Apple Music:
In the meantime, these limitations mean that any music app that attempts to play Apple Music tracks will be seriously limited, require odd workarounds, and behave problematically depending on user behaviour. In the spirit of giving users a quality experience, we’re stuck with the same limitation that other sophisticated audio apps have today: no Apple Music.
The explanation is a bit technical in places, but I think we can all relate to some limitations he details: apps can't modify Music playlists on the user's behalf, queue management is severely limited, and fading a song out is a private API.
There could be an entire ecosystem of music utilities and alternative players based on the streaming service – think how professional DJ apps, tagging services like Shazam and SoundHound, or music discovery apps could take advantage of a direct integration with Apple Music. I hope Apple will consider some of these suggestions for next year.