Personally, the sorts of people I recommend MBTI to are the intelligent people I would like to learn more about. I've never recommended MBTI to someone I thought was devoid of intelligence, and I've never met an unintelligent person irl who was interested in MBTI. I've recommended MBTI to simpler (ie less troubled) souls, and they almost always turn out to be Ss. Simple is not the same as unintelligent, however.
The point of which is that I've never met a known NF irl who was unintelligent. They usually have plenty of rope to hang themselves with.