You are very fortunate to never had the displeasure of having to interact with profoundly stupid people. Not ignorant, not uneducated, but genuinely stupid and slow people.

E.g., People for whom significant, immediate, unexpected mechanical feedback in operating something simple, like window blinds, wouldn't cause them to consider whether they might be doing something wrong, and instead continue operariting the blinds in the wrong direction until they snap and break, genuinely being unaware that they were doing it wrong.

People who are genuinely lacking the common sense you'd expect a human to have, not even with any cognitive disability or learning disorder of any kind - just genuinely stupid but otherwise ordinary people.