Can't say for them, but for me I have a single playlist 6,994 songs on shuffle. I try to add songs every week, haven't recently as I also should be moving off of Spotify.
Spotify "radios" (playlists that are generated on-the-fly once the thing you were listening to ended), recommendations (Spotify’s weekly playlists) and top 50 <country> playlists, browsing the "similar artists" tab on artists I like, browsing the "discovered on" tab to find playlists. Then, when I like a song from an artist, I usually listen to at least their most recent album.
Last week I found a Russian artist in a playlist I follow and I listened to all their albums. I don’t know how to pronounce their name nor the title of any of their songs, but it was a nice background music for coding since I don’t understand a thing of the language.