Everything has an expert. There are experts in sports, in arts, in sciences, in law, in medicine, in culture, in language, in engineering, in entertainment, in business, and in countless other venues. It is incredible what you can now get a masters degree or doctorate in. Whenever there is uncertainty or a question people run to experts. There is a certain comfort from hearing from an expert, a soothing quality in knowing that someone else must have a plan.
However many experts from many fields are dispensable. They may have a degree from a nice university, a sparkly diploma that they can hang on the wall, but unless the expert can demonstrate value by reproducibly obtaining better results than a non-expert, the title is disposable and the diploma meaningless.
There are some tasks or problems where it is perfectly alright to let a non-expert take a crack at it. If you are unsure if the person who is washing your car knows what they are doing you are unlikely to make a big deal about it. At the worse you may be out a few bucks and have to wash the car yourself. Likewise, you can have a non-expert give you an opinion on French politics, the quality of baked goods, or the weather with the downside rather limited to a waste of time and having to do the work or research yourself.
On the other hand, there are some tasks where an expert dramatically raises the probability of success in a field where failure is irreversible and catastrophic such that few would even think of trying something ad hoc. No one would look for a neurosurgeon on craigslist or let someone cut you who had not been to medical school. It is not to say that they might not get extremely lucky and do the operation correctly, it is that the likelihood of them doing it correctly significantly increases with the degree and the experience. Likewise anyone could get extremely lucky and fly a commercial airplane, perfectly nailing the takeoff and the landing, but no one is going to get on that plane. In both these cases having an expert is critical because the expert title ensures a level of previous experience and skill in a setting where the consequences are devastating and irreversible.
Now that we have established that the appeal to the expert is applicable in some, but not all situations, we also must highlight the fact that the appeal to an expert is not the same as the appeal to the expert. During Covid-19 there have been many posts on social media giving advice and information with the tag or implication (by attire, scrubs, white coat, etc) that they should be listened to because they are a physician, nurse, podiatrist, medic, or PhD in science. In general most of these “experts” are not experts in public health and infectious disease. This does not mean that they should not be listened to, but rather that the evidence that they provide should be weighed, considered, and if it is good, then accepted. Public health and infectious disease are only as good as the evidence they utilize. In this case, saying “listen to me I am a physician, nurse, medic, podiatrist, PhD etc.” without any evidence is unacceptable and akin to claiming to be an expert in economics because you have a piggy bank. Evidence trumps “expert” opinion in this, and every pandemic.