All the Tumblr aesthetics for the houses pretty much show how they manage to be really broad and not well defined yet you can still say "
that doesn't belong!" pretty easily. Here's one of the tiny pictures:
Ravenclaw aesthetic
Commenter: could also be a Slytherin aesthetic
Me: NO.
(Although some of the ones that are clearly intended as one House just seem wrong anyways so I don't blame people for trying to change them, and the angel in that one could fit in Slytherclaw ones easily, Slytherdor not as much)
I also think the houses work better that way. They're like teams. It's better not to have a bunch of clones who can't cover for each other.