I don’t use this, or Spotify, but those are the only two systems I’ve heard people give praise for the recommendation engine — I suspect that its because music playlists are almost equivalent to a rating system.

That is, the user is capable of efficiently informing the engine of their taste, and there’s significant incentive for the user to consistently re-evaluate their ratings (playlists), so it can be trusted as up to date.

Another very important aspect is that playlists are useful enough to the user that they actually want to maintain it.

For example, amazon, netflix and pornhub all have rating systems, but they’re not at all useful. The interface isn’t useful enough for reviewing and reflecting on, its not comprehensive enough to keep as a primary list (because it only covers what they offer, which is very limited) and there’s of course no impact on the recommendation engine (because the rating systems are not worth using; chicken and egg). No sane person would touch the things (beyond “upvoting”, which isn’t significantly related to taste)

Imo ratings are absolutely vital to useful reccomendation, but they’ve been totally neglected

The radio stations off custom playlists are indeed pretty good, but the recommended ones on the home page are often horrendous and very short (songs will basically get repeated after less than 1 hour).