We Catholics "enjoy" a separatist group whom we call, "Cafeteria Catholics."
Just as one walks through a cafeteria line and picks out what one wants to eat and leaves what one doesn't, the Cafeteria Catholics choose which teachings of the Church they want to believe and leave the others alone. In Biden's case, he is OK with abortion, calling it a "right to choose."
Catholic childhood education is so pervasive (assuming you went to a parochial school) that one gets the impression that one is "Catholic" in almost the same sense that one is "Italian," or male, or blue-eyed. It is - one imagines - immutable. And this is why even those who reject whole sections of the Catechism continue to think of themselves, and call themselves, "Catholic."
But Joe Biden is no Catholic. He can go to church until the cows come home, but no person who supports killing babies is a Catholic.