If Taylor Swift pulls out of Spotify, but Spotify's users are listening to "Discover" not "Taylor Swift", then Spotify is afforded with the opportunity to play "something that sounds like Taylor Swift." And god knows there are enough hungry and talented bands out there looking for a break...
Admittedly, it's been awhile since I was in grade school and marched in musical lockstep with my peers, but it seems as decent of an idea for disempowering major, advertising-heavy record labels as anything.
I have both, and for discovery spotify is way behind Apple Music, and i often find things on Apple Music that i cant get on Spotify. But one of those factors maybe my taste, but i have one friend with totally opposite taste to me that has had the exact same experience.
You are not using discovery really if you are doing the finding. It should be automatic in that just play one of the daily or weekly lists and music that you like (some old some new) should be played.
I tried Apple Music for its free trial and switched back to Spotify as I just can't be bothered to choose what I listen to myself.