Yup -- the first thing public health students learn is the WHO definition of health: "Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity." In my clinical trials course, equal emphasis was put on extending life and increasing quality of life (e.g., as measured by quality adjusted life-years (QALYs)).
When I was a kid childhood leukemia was a death sentence. These days survival rates are in the 80% and up range.
The goal isn't non-dead sick people. It's well people.
Attacking that problem doesn't mean that you can't attack the problem of too many people too. Hopefully in a more productive way than having a horrible, lingering, painful disease solve it for us.