Now, there are internet attempts to replace the function of the expert at the little store. For example: Pandora. "If you like Jimi Hendrix, you must like Jeff Beck." But I don't use Pandora, for this reason: Jimi Hendrix might inspire me to listen to Thelonious Monk. Or gnawa music from northern Africa. Or Bob Dylan. With someone like the guy at the little video store, you can have a conversation: "Actually, it's not Grace Kelly I'm after, it's the cinematographer who did this movie. Can you help me out there?" "Oh, sure... [etc.]"
End of rant...
You make a lot of good points, but I can't relate to your complaint about Pandora. I have gotten turned on to a lot of different music and artists by Pandora's music genome approach, that I would otherwise never heard of. For example, Donny Iris lead me to Sun Dial -- never would have heard of them otherwise.
To put it another way... If indeed listening to Hendrix might inspire you to listen to African music, how would you even know? Unless you have ready access to African music, or are already familiar with it, there's not really any way Hendrix could lead you to African music. On Pandora, Hendrix might lead you to Robin Trower or Frank Marino, who then might lead you to someone else.