Anytime I learn about bodily functions I become more and more aware of how shit it's engineering is. Works amazing, sure, but try and fix or debug anything? Good luck.
I really would not call my body bad engineering, just because I do not understand how it works in detail.
Rather the opposite, the more I learn, the more amazed I am, how awesome it all is. The complex interactions of chemical, electrical and physical components. (And who knows, maybe even quantum field elements.)
I could not design anything remotely complex at all.
Also, I debug and fix my body all the time, or rather, my body does this mostly in auto mode.