“I also have no idea how anyone can make anything but a superficial comparison between hip-hop/rap and disco. Night and day.”
You ignore the fact that quite a lot of hip-hop is people talking/singing over old disco recordings.
They use other types, too. It really doesn’t matter what they sample; that doesn’t make it the same type of thing.
(BTW, I can appreciate some hip-hop, but I can’t take it forever because it all seems exactly the same, same beat, same monotone. Rap is worse because it’s more intense and violent.)