I don't know why you think missing exits is in any way indicative of someone's intelligence. I've missed plenty of exits, and let me inform you of something: it's not a big deal. Like, at all.
You know what stupid is? It's focusing on things that are not a big deal.
It's indicative of not paying attention to your surroundings, which, when you're piloting a 4000 lb hunk of metal, could be considered a stupid thing to do.
You're rationalizing. My wife misses exits constantly, but she does it safely--she's paying attention to the cars around her, but following a habitual route to some other place.
You know what stupid is? It's focusing on things that are not a big deal.