that's.... a good question. He knows more about magic and knows as much about magic as any of these other dudes know about their fields of interest.
But he really knows absolutely nothing about the "regular" field of knowledge to make it on the list.
It's also the reason I say Doom is smarter than Reed. You know 7/8 of what Reed Richards knows, you know stuff Reed can't even figure out even in those areas, then you know 100% more of a WHOLE OTHER AREA of expertise, and you're considered an expert in that, too.
Doom's magical library. Reed knows nothing in this room.