Your expectations are unreasonable. Most doctors are practitioners, not researchers. They are applying existing care protocols rather than collecting data and coming up with statical tables. Good doctors will follow evidence-based medicine practices where applicable, but individual cases often diverge from the standards.

There is a huge amount of medical research going on but the field is so complex that progress is necessarily slow. Carrying out long-term studies in humans is extraordinarily expensive because researchers need large study populations to extract a useful signal from the noise caused by confounding factors. You could make a case that doctors should intervene earlier to prevent chronic conditions while patients are still young rather than waiting for more serious signs and symptoms to develop. But on the other hand, the available drugs often have significant side effects that impact quality of life or cause other harmful side effects. So it's not an easy call and there are still many unknowns.