You are confusing sprinting and marathon running. The human foot and leg is NOT optimized for sprinting ahead of a tiger nor for sprinting ahead of another human. It is optimized for running at a slower pace, non stop, for days. LITERALLY.
A perfect specimen of human being is unmatched in the animal kingdom for non stop running and walking. Not counting swimming and flying, a human being can traverse more miles nonstop before dropping dead than any living thing on the planet.
Very few humans are perfect, or optimum specimens. As a former long distance runner, I can tell you that competitive long distance running will expose minor defects and deficiencies in body structure like nothing else known. Things WILL fall apart if they are not perfectly in balance with each and every other component.
For instance, I learned that I have a defect in my big toes. My big toes do not bend backwards as far as they should. Also, I have a deficiency in skin thickness and pad thickness in the bottoms of my feet. In the long haul, these things created chronic problems for me when running very long distances.
Because the big toes do not flex backwards far enough, there is greatly increased pressure applied to the pads of my big toes. This causes my shoes to wear out very rapidly under my big toes. It also caused the pads on the end of my big toe to flatten and spread out and become compressed...and tendon tears just below my kneecap are easily acquired. other problems can also be attributed to the big toe defect.
feet are INCREDIBLY important. There’s a reason why the army used to ban folks with flat feet from serving.
But where did the genes come from in the first place? How many mutations do you see that make legs (two at a time) longer, stronger and coordinated? Are your children, if taller than you, because of mutation? No because the genes were present in them already and because of good nutrition.
On the other hand you will see many, many defective legs because of mutation.