Stupidity and low intelligence are totally different things. You can be of low intelligence for any number of reasons: being starved of oxygen at birth; sustaining a traumatic brain injury; any number of illnesses. Through no fault of their own, not everyone has the capabilities to be a doctor or a lawyer or CEO or whatever your particular brand of success is. This is in no way a 'character flaw', and to suggest that it is is highly offensive.

Even the most intelligent person does stupid things, but some people could turn stupidity into an art form. I don't know about character flaws. It's not a thing that would ever cross my mind to think about someone.