Agreed. That's probably because of just how much manual work went into it:

"Each song [representative of other songs in its group] is analyzed by a musician in a process that takes 20 to 30 minutes per song. Ten percent of songs are analyzed by more than one musician to ensure conformity with the in-house standards and statistical reliability." https://en.wikipedia.org/wiki/Music_Genome_Project

YouTube’s used to be really excellent. I discovered so much good music when it seemed to work by automatically cueing songs or videos that other people who enjoyed the current video had enjoyed as well. They seemed to make a change a couple years ago to cue items I had previously watched instead. So now, instead of fresh and interesting items relevant to my tastes, it just plays things I’m already familiar with.

Pandora, if I'm remembering correctly, also has a feature that Spotify lacks, which is to say "I don't like this" for a piece that it chooses. Although I couldn't say how much that influenced its later choices, it feels better as a user to be able to convey it.

I know for several of my "stations", they kept trying to suggest Coldplay. I'd constantly give them the thumbs down as I didn't feel Coldplay matched what I was going for. It didn't seem to affect their later suggestions.