Spotify is designed to make itself indispensable. It offers up endless choices. It keeps playing when the track or album you’ve clicked on is over. It tries to predict your tastes, so you keep consuming content—er, music—for as long as possible. But at the end of the day, it’s just a format. And Spotify may not be the right format for everybody. That became clear recently when Spotify CEO Daniel Ek shared a disturbingly narrow vision of how music and musicians should work. In an interview with the website Music Ally, the tech billionaire responded to criticisms that Spotify doesn’t pay artists enough by pointing to the artists themselves. “[S]ome artists that used to do well in the past may not do well in this future landscape, where you can’t record music once every three to four years an...