Though we poetically think of humans as somehow divinely designed, or flawless in someway, after many millions of years of evolution we are a big bunch of hacks and compromises. Highly variable build quality. Waste disposal and procreation packed into one small space. Spine still getting used to walking and running. Birth itself is hazardous.

And our cognition is horribly skewed based on ancestry with primates. The social systems that drive our incentives (including quality) are hacked up. So much of that could be enormously different by now and isn't. So how do we expect more quality as an output?