You could say "Spotify's algorithm", but you need to help it. It is more their links between artists that I use, and the general availability of a lot of artists. (Not as many as on YouTube.)
If I have found a lot of great, new music this week, next week's "Discover Weekly" and the albums recommended in "Home" are better.
Most of the music I find is by looking at the tracks I'm already playing: Maybe I only heard one song from an artist, maybe I only ever listened to their old stuff, or maybe I only ever listened to their new stuff. Maybe it's a remix, and the featured artist is the one I like, so I listen to their top songs.
I've learned that whatever one-hit wonder people have -- the song that everyone plays 10 times more often than their second-most popular song -- is often a good choice if you're assessing a musician. But if you like them, it's also likely that your favorite song isn't everyone else's.
I mostly listen to electronic music without vocals, so I can play a lot of random music while I work, and occasionally something sticks out in a good or a bad way.
Last year I spent 65000 minutes listening to music on Spotify.