When you were at a university (without grade inflation), how big was the portion of students you felt truly mastered each subject? 5%? Would you expect something different with MDs? Your doctors are statistically most likely average or below average, so is their advice. They likely graduated by memorizing a snapshot of medical knowledge that was current when they graduated, with updates coming in with far lower weight. If you want great advice, get two persons - one a recent smart graduate, the other experienced one with great stats. I hope at some point many of those murky decisions could be automated away with machine learning soon.