If you have a profile and a playlist that consists of things you like (can be the Liked videos one): 1) Nuke the built-in youtube history 2) Download browser

If you have a profile and a playlist that consists of things you like (can be the Liked videos one): 1) Nuke the built-in youtube history 2) Download browser plugins that disable the "are you still watching" popup and one that lets you watch videos faster than 2x 3) Click on your playlist, make sure autoplay is on 4) Leave the entire thing overnight so that the history fills up This didn't fix the problem, but it at least made it bearable and improved the quality of recommendations. I also recommend the "Channel Blocker" extension, works a lot better than built-in functionality