That would only work if the learner is so motivated that they spend months poring over medical and biology textbooks to understand enough background, and then l

That would only work if the learner is so motivated that they spend months poring over medical and biology textbooks to understand enough background, and then learn how to read scientific papers and interpret studies for statistical significance, to get up to date on the latest research. And of course they also must have the aptitude to do all that, to get to the point where they can start meaningfully questioning the doctor's recommended course of action. Otherwise, they're still just going to have to trust the doctor.