Consider just the challenge of defeating the obesity epidemic. Better diet improves energy and massively increases, again at the population level, the amount of raw thoughtful hours are available to a country.
This is even more widely applicable in global health where health initiatives can also be important components of social change. Women's/sexual health is tied deeply to women's rights which is a leading indicator for social revolution.
While medical breakthrough that change the space of healthcare at large might be rare, there's a lot of room instead for the kind of breakthrough which changes how people receive and are impacted by the healthcare knowledge we already have today.