Look you're being just as hand wavy, and your sterile gut idea is a bit of spherical cow. We will never be able to sterilize our environment to the point where

Look you're being just as hand wavy, and your sterile gut idea is a bit of spherical cow. We will never be able to sterilize our environment to the point where we can easily maintain a sterile gut. No one fully understands the human microbiome, including you. Are there any case studies of people maintaining a sterilized gut and living healthier lives? Therapies like fecal transplant or helimintic therapy actively introduce third parties into your gut with positive outcomes. Which at least suggests that bacterial balance in the gut is important for some people.