Milk was ok, but it used Slack as its back end. Milk was the bridge of radio playing that Spotify/Google needs. Pandora would be the closet to it. Even SirrusXM's streaming app is very close to Milk, and includes nice advanced tuning features. (popular vs ecliptic)
So we have a mix of music service that really are mashup or good in certain areas, discovery (slack/pandora), playlists (google/spotify), buying (amazon/google/itunes), podcasts (stitch/itunes/spotify is trying add this), tracking songs (Last.fm).
Slack was first to offer off network caching which was great, but when spotify offered this, I dumped slack and went Spotify full time. I dropped Pandora for slack also due to better mobile offering.
So now, I'm down to Spotify, Last.fm (paid), and amazon for buying my music. Google gave me Google Music for free because I bought Youtube Red (no commercials), Amazon gave me free Amazon music with Prime, but its interface is horrible, even for buying. Google music design is horrid.
Spotify runs well on my linux laptop, android phone, and windows PC, lists are synced. Now if they could add DFX into the app for linux/android, I'd be in paradise, the fidelity option is a good start.
Still feels like the dark ages. I had a co-worker try to start a multi app suite with all the different features including identification (like shazam/musicID), but it was too early in the market during the days of rhapsody.
Wouldnt say we are even close to being perfect in the music realm. There is so much good music on Spotify, but it needs an translations for non-english band names and music. Also really needs better ways to find non-american music. Theres so much out there, and they keep us in a tiny walled garden.
Oh, and spotify allows you to follow distribution labels, which is AWESOME if you follow great producers. But that could be way easier to use.