Who are we to say the mechanisms of biology are “overfit”? Maybe it would be nice if our personal machinery was more robust, but that robustness comes at an evolutionary cost. The greater force that is life on earth as a system for regulating planetary energy dissipation does not care about the needs of the individual. It does not care about the fashions of the millennia. Its sights are set much farther and its history much deeper than that
For more complicated organisms, robustness comes in the form of cellular turnover, and regenerative healing in response to injury, at least in youth. I wonder though if single celled organisms have or even need such a function.