Problem is people are stupid, lazy, and/or corrupt in all fields, including the medical field. It's a big part of the reason why anti-vax and anti-science movements exist: partially from that retracted study that initially claimed autism was caused by vaccines, partially from cases where the "expert" is following some obviously flawed dogma (like "people that young don't get shingles"), partially from corrupt studies being exposed later on as fraudulent, like the tobacco industry "studies" that claimed smoking wasn't dangerous.

The part that sucks is that I don't believe there's a good solution to this because that set of flaws can hit either side of any argument.

I also believe that it's related to our ability to progress itself: humanity kinda brute forces beliefs and it sometimes works out for the better, when people like Galileo, da Vinci, Newton, or Einstein think everyone else is missing something or flat out wrong about some stuff and revolutionize our understanding of physics or what's possible with machines. Sometimes it works out for the worse, like the anti-vax movement, flat earth, anti-Semitism, or believing that opposing oppression and genocide is anti-Semitism.