I suppose those of us who have never lived in a place where flouride is added have bad teeth.
If you eat heaps of sugar and don't practice proper oral hygiene no one can help you.
My dentist who is an older chap has commented that the addition of fluoride is creating a cavity free generation. My children have never had their mouths drilled. I have a filling in each molar. Their father's situation is similar. Clearly, genetics only go so far. Fluoride can make a difference.