[Potando]

Not stupid, but they either didn't understand or relied on the placebo effect and didn't perform experiments that were actually useful at distinguishing helpful from harmful or useless medicines - AND communicate that information to others. When an ancient remedy turns out to be useful, it's not useful until we rediscover that it actually works. The idea of science and sorting out mysticism from reality is fairly new in most of the world. In China, doctors in public hospitals still prescribe untested herbal remedies and diagnose diseases without any idea of the effectiveness of what they're doing. Patients just trust authority, tradition and popular belief. You could argue that the same is true to some extent in the west today too - see general "have some antibiotics" prescriptions, and cough and cold medicine.