The sort of stuff that clogs up the Browse tab. If I check quick mine now, there is a hefty amount of rap, amapiano, R&B, soul/Christian, African, Afrikaans etc. stuff. My interest level is about zero in 99.9% of that and my listening history would reflect that. Apple really should do a better job in how it shuffles its curated sections around. Right now I wonder if it does anything besides geo-based filtering.
My Made For You playlists are generally good, and track-based stations are consistently good too. My personal mix station is okay but the newer Discovery one is god-tier for me.
Most people I know don't seem big on their personal library when it comes to music streaming. For me my library is essential (Spotify trashing their library is why I switched to Apple Music), and it's meticulously maintained. One of the main things I dig about Apple Music is its best-in-class library management.
If you're mostly just browsing for curated playlists and stations, I can see how the lack of personalisation in how things are presented would get extremely irritating.