There are different degrees of idiocy.
Callis has the emotional intelligence of a potato (He is getting better)
Novus has a motor mouth and poor impulse control even when he is book smart.
Robio is kinda dumb, but he has street smarts.
Berula is extremely intelligent, but as little to no regard to some societal norms
Alexa is dumb as a brick, but balances it out by being built as a house, made out of bricks.
Falco isn't dumb, but he is arrogant enough to ignore warning signs.
Parvus and Foedesius are fucking idiots.