> In terms of mass-market success, goodness of recommendations is like, #12 on the list of must-have features
Well, maybe that's why they generally are not so great.
On the other hand, Pandora has traditionally existed with playing music that you'll like, but didn't explicitly select, as its reason for existence. Maybe that's why it seems to do a better job at this than other streaming services.
#1 is "It must have all of the music", which is really a lawyer problem, not an engineering problem.
(#2-#11 are just variations of "No no, I mean all the music", "Does it have really old music, like X?" "What about really niche music like Y?" "Oh, oh, what about Z? I bet it doesn't have Z.")