On some levels I see where you are coming from. However please consider that swimming is not just learn one stroke and you know them all.
Track and Field is essentially made up of events that consist of Running, jumping and throwing. Learning the events of each is a feat in itself. So is learning and mastering each swim stroke and learning how to win the distance you are swimming that stroke. There is A LOT more to swimming then meets the eye.
I do get what you are saying, but I think you are short changing the athleticism of swimmers.
Is Michael Phelps the greatest Athlete of all time??? I don't really know..... but I do know he is the greatest Olympian of all time.....so say the record books