I think the miscommunication here is in the function. I agree with you, that you can use Spotify to find all kinds of music, and even incredibly niche music if you dig around. What the user you replied to wants is to be able to find that incredibly niche/hyper-specific music with a single search query.

If that user wants to discover music like the band Tool, but has never heard of the band Tool, they want to be able to type “complex polyrhythmic prog metal with tribal trance undertones” and have it spit out Tool, Lucid Planet, etc. Spotify can’t do that. Tool is popular enough where it isn’t a great example. But even still the best you could do is look at their curated lists for prog metal and polyrhythm and come up with what you want after skipping through some bands. And you would find things like Dream Theater and Periphery on those playlists which couldn’t be further apart from Tool and each other, despite sharing a general genre.