There's full external library management going on on Spotify. Tracks are removed from personal private playlists (some of the best). Tracks are inserted at old dates in personal private playlists.

Removing what I didn't add myself in my entire Spotify library is a full-time job already. Guessing the many tracks that are gone isn't even doable. Spotify has me checking just one small playlist all day. I can notice something I didn't add, inserted at old date, every day. I have to actively review my tracks instead of just enjoying music.