I can't tell you how many of the streaming services will see my Black Sabbath play history and immediately recommend, "If you like Black Sabbath, you should love...Slipknot!" But I've never had a real person make that mistake, because a real person who looks at my last.fm history and has an understanding of the genre says "Gee, this guy has plenty of Black Sabbath, Iron Maiden, and tons of doom metal on his list, but doesn't have Slipknot, Korn, or Pantera in his history. Maybe that's intentional."
Human review and recommendation still beats algorithmic recommendation by a mile if you have discerning tastes.