Shirts with button-down collars are not dress shirts

Shirts with button-down collars are not dress shirts. They’re sports shirts, so wear them with a sports coat. Polo players used to button their collars down so they wouldn’t flap up in their face while they played. (Are you beginning to sense a theme here? Fashion rules are largely dictated by what English gentleman and nobility did generations or even centuries ago. Sports coats? You wore them during sport, i.e. hunting. Regimental stripes on ties? They indicated your regiment in the British military. And so on.)