Yeah last time I used Pandora, every station would inevitably turn into "freehunter's favorite songs". Rap station? Well Run-DMC did a cover of Walk This Way, and Linkin Park is kind of rap and Beastie Boys did a lot of rock songs, and now suddenly I'm getting a lot of rock in my rap list, and rock melds into pop pretty easy, and now suddenly my rap playlist has Katy Perry and Kesha.
And thumbs down is always way too harsh in any algorithm you'll find, because there's no way of telling the algorithm why you didn't like it. If I thumbs down Thunder by Imagine Dragons, how does it know I really do like Imagine Dragons and that album was good and the genre was good, I just don't like that one song? And if I thumbs down Good Riddance by Green Day how does the algorithm know I love Green Day and I like that style of music, but I just have a really negative emotional attachment to that song and I don't want to cry right now?
Context is super hard but super important. I listen to a lot of ambient music at work and now my Apple Music and Spotify suggestions are all ambient music, even though I don't listen to that genre for pleasure.