If the human body didn't heal itself, how'd you be doing rn?

This is just too unrealistic. I mean, some people actually suffer from conditions where they have a really hard time healing wounds, like lack of plackettes. And some people bruse extremely easily. But if you were unable to heal at all, you would be long gone. Kids get scratches all the time, and even one scratch would lead to an infection that would overwhelm you immune system.