So Frumious. If you could have...how would you have done better
If evolution wasn't a restriction, and we want to retain the overall morphology, we could rework the eye so the blood vessels and nerve fibres run under the photosensitive cells and the blind spot is eliminated, and the photoreceptors could face the direction of incoming light (octopus & squid evolved a camera-type eye independently, and got it 'right').
We could remove superfluous teeth now our jaws are shorter, and have multiple replacement sets.
We could sort our backs out so they're better suited to an upright bipedal gait.
We could sort out the urogenital area so the anus is further away from the genitals, reducing the incidence of infection; move the male urethra so it passes around rather than through the prostate, separate urinary output from seminal output; move the testicles inboard by reorganising the blood supply to keep constant temperature; sort out the female pelvis and birth canal to ease childbirth and still allow efficient gait; fix the structures between ovary and uterus to prevent ectopic implantation.
We could rearrange the nasopharynx to better separate food input from respiratory input, preventing choking, reorganise the lungs to a counterflow system, like birds.
We could redesign the knee and fuse the fragile bones of the foot to improve resilience and strength.
We could fix the recurrent laryngeal nerve so it goes directly from the base of the skull to the larynx instead of looping under the aorta(!).
It would be nice if we could switch on the gene that used to produce vitamin C, so we're not so dependent on external sources.
We could fix our lousy thermoregulation so we can maintain thermal homeostasis without sweating so much; fix sinus drainage; re-enable nerve and limb regrowth; tidy up the brain, so the left & right hemispheres deal with the left & right sides of the body, move the visual cortex to the front, nearer the eyes, and so-on...
There are plenty more, and probably thousands at the level of cell biochemistry, not to mention the mental side - cognitive biases, flawed heuristics; flaws of the senses, perception, processing, memory storage & retrieval; behavioural fragility and faults. Oh, and genetic diseases...
The flaws are mostly the consequence of evolutionary adaptation and repurposing.