Some people think that humans are very badly designed. But they do not have a better one.
For example, I was assembling an electric motor and I need the dexterity of two hands, four fingers and two thumbs to hold parts together, manipulate the screws and nuts together.
So let me see. Three hands would be better for this job, but the extra hand would get in the way when running from prey. Extra thumbs. Well we all know the saying "I was all thumbs".
The sensitivity, the self-repairing ability, the finger-nails that are just right. The same applies to any other body functions.
Mammals have used bacteria to work inside their stomach to produce energy. We have amazing immune systems to fight off the bad pathogens and parasites.
Our voices are capable of songs and language that outstrip any other creature. And beautiful to boot. We are, in all respects, "just right" for an incredible range of tasks, sports and arts.
My father lived to 95 and his body held up very well, until the last few years, and this despite a hard life and being exposed to many toxins and carcinogens.
If there had been any inherent problems early in our evolution we would not have turned out the way we did. It has been a miraculous journey of evolution and survival. Even the planet and solar system had to be just right.