"medical dogma may be more prevalent today than in the past because intolerance for different opinions is on the rise, in medicine as throughout society."

I think a large part of that is perceived liability. Remember when Covid19 first hit, there was a doctor claiming an early treatment prevented his cases from getting bad. That one sticks with me not because I think he was right, but because the response was "That's not an FDA approved treatment for this." It wasn't just him, but others as well. The problem is there was NO approved treatment for it. To me it looked like doctors being afraid they'd get blamed for doing anything off the beaten path, so much that they were afraid even when there was no path. Such is the world we live in...

So much of the bad advice that was eventually proven wrong was exactly that: advice that seemed to make sense based on our understanding of biological processes, but was never actually tested.

Stuff like the bad advice about avoiding eggs because they are high in cholesterol (turns out for the vast majority of people can eat eggs without negatively impacting blood cholesterol), stress causes ulcers (it was just believed that the stomach was too acidic to allow bacterial growth, until someone really looked), etc. The interesting thing is how strongly the existing "medical establishment" dug in when they had no actual studies to back them up.