I don't use Spotify, but on a similar note, my lone positive experience with any kind of recommendation algorithm has been with Apple Music/iTunes. Perhaps it's because I have used the platform for as long as it's been around, and have always been actively creating playlists, rating tracks/liking tracks within iTunes itself, thus ensuring their "genius" algorithm has sufficient information on me, but I have consistently managed to discover a lot of great bands/tracks/albums from it. Especially over the past year or two, it's pretty impressive.