There are over a million licensed physicians in the US. If we assume that each one interacts with five patients per weekday, then in the six months since you had this experience, that would conservatively be six-hundred-million patient interactions in that time.
Now, obviously none of this math would actually hold up to any scrutiny, and there's a bevy of reasons that the quality of those interactions would not be random. But just as a sense of scale, and bearing in mind that a lot of people will easily remember a single egregious interaction for the rest of their life, and (very reasonably!) be eager to share their experience with others, it would require a frankly statistically impossibly low error rate to not be able to fill threads like these with anecdotes of the most heinous, unpleasant, ignorant, and incompetent anecdotes anyone could ever imagine.
And this is just looking at the sheer scale of medical care, completely ignoring the long hours and stressful situations many doctors work in, patients' imperfect memories and one-sided recollections (that doctors can never correct), and the fundamental truth that medicine is always, always a mixture of probabilistic and intuitive judgement calls that can easily, routinely be wrong, because it's almost never possible to know for sure what's happening in s given body, let alone what will happen.
That E.N.T. wasn't up to date on the latest research on allergies. They also weren't an allergy specialist. They also were the one with the knowledge, skills, and insight to consider and test for allergies in the first place.
Imagine if we held literally any other field to the standard we hold doctors. It's, on the one hand, fair, because they do something so important and dangerous and get compensated comparitively well. But on the other hand, they're humans with incomplete, flawed information, channeling an absurdly broad and deep well of still insufficient education that they're responsible for keeping up-to-date while looking at a unique system in unique circumstances and trying to figure out what, if anything, is going wrong. It's frankly impressive that they do as well as they do.