Dimorphic males who are exposed to higher levels of testosterone develop smaller waists and broader shoulders. Leading to a higher shoulder to waist ratio. There are studies which show ~80% of attraction is shoulder to waist ratio.
IDEAL SHOULDER TO WAIST RATIO is approximately 1.85-2.00. The higher your ratio is without working out the better. It will also mean achieving the ideal will be easier.
HOW TO FIX: as this is primarily bone this is near impossible to fix. Working out will rarely improve this significantly. See the man on the right, no matter what, he will be unaesthetic due to a lack of a dimorphic frame, skinny broad shouldered males will always look more aesthetic even if they are untrained