As someone who is actually an expert in a subfield of medicine, not only do doctors not understand it at all, but the experts making guidelines often recommend the exact opposite of what is the best treatment for the patient, usually for liability reasons, but occasionally for true lack of understanding. The quality of research is so poor that often times there are more flawed studies showing X than proper studies which would show ~X. Other times there is no research on the matter at all, and the conventional wisdom (even among experts!) is incorrect. For fields where practice and theory diverge, like an experimental surgery with sparse research, the surgeons know that the guidelines are useless.
What you yourself _have_ to realize is that the expert researchers who are in a position to create and inform guidelines are themselves not some kind of 'super-experts' who know everything better than normal experts. They're just researchers in a political position in a bureaucracy.
I don't exaggerate when I say that an average HN reader could write better guidelines for patient outcomes in my subfield, with no prior training, simply by reading a few studies and observing a practice.
Now, does any of this apply to internal medicine, specifically covid? Probably not. But when the data is anything other than crystal clear, you should not assume the expert guidelines are anything more than some guesses by guys in a room. The consequence of knowing this is that all guidelines and consensus is suspect until you see the data yourself, like TFA outlines. In this case it seems true that Ivermectin doesn't cure covid. But with my experience, the exact opposite result could have been shown and I would not be surprised whatsoever; experts saying it doesn't work does not constitute in my eyes anything other than noise until the data is clear.