What's wrong with being stupid? Fools are born stupid. In today's society, as you think, there are too many smart people, but most of them are unhappy. Because they want too many things, they lose their understanding of life. Your sister-in-law may be a little "stupid", but on the other hand, she doesn't have much mind to live a simple life, and she won't put too much pressure on your brother or have any contradiction with your mother. This kind of woman lives a down-to-earth life. Your brother has a vision. You'll understand when you get married.