They suck, in my 2021 Year in Review my top listened to song was a song by a band neither of which I've ever chosen to play.

I miss Grooveshark's slider that let you choose Familiar - Explorative on their automatic playlisting. Honestly I think ANY algorithmically generated feed needs this (Insta, YT, Spotify, whatever) to prevent people getting sheltered into sameness who would prefer some variety.