Indeed, but I think that the point is that you shouldn't give up and let everything go.

Indeed, but nobody can be quite sure that they will win the lottery and therefore can afford to kick back and do it the easy way. Moderate exercise, eating more of the good stuff, and letting go of some unhealthy habits have big impacts on overall well-being that are hard to describe. Simply put: not sick != healthy

A healthy lifestyle improves outcomes pretty much regardless of genetics. Genetics just determines the ceiling.