The only good recommendation engine is Pandora's Music Genome Project. It's the only one that auto-queues songs that sound like what you've seeded. Every other service will play you other songs from the same artist or genre, even though they sound nothing like what you've seeded. And then they pepper in other things that have nothing to do with anything - the "sponsored" crap.

It's just too damn bad that Pandora refuses to keep up with the competition and add higher quality streams. It sounds noticeably bad by comparison when using modern sound hardware. I just use them for recommendations now, so that I can curate my playlists in services that do offer high quality sound. They could easily be the only music service I pay for, but I'm not going to pay for subpar sound.