I have noticed an interesting phenomenon around TOOL. If you start a playlist on Apple Music from TOOL it will start playing everything from Metallica to Nirvana. A lot of people like TOOL for a million different reasons and Apple doesn't know any different except for the overlaps in taste. If you play a Mike Patton band, such as Mr. Bungle though -- you will get some TOOL in your playlist -- because both bands are esoteric and often challenging.
I'm looking forward to the day (or wishing maybe) when my app considers these factors. For me the issue isn't discovery, but rather I want my robot DJ to vibe more closely with me.