In one sense I agree with you, although in another I disagree.
What's any doctor going to say when a patient comes in saying "I just quit smoking and I'm dizzy, anxious, and I'm having trouble sleeping at night"
The answer is a great big DUH... because these are common symptoms of withdrawal from tobacco.
You can save yourself a hundred to a hundred and 50, by first finding out what everyone who quits feels like in the beginning, and only going to the doctor if your symptoms seem in some way unusual.
It's really common sense. In a way yes, it's self diagnosing and is not always the safest bet, but all a doctor is going to do is look at a patient and decide whether or not they are experiencing symptoms that are common to the root cause (or not) and, if the symptoms are severe enough, prescribe something to alleviate the worst of those symptoms... or, do further testing if the symptoms are in some way unusual..
A person with some measure of intelligence can figure out that second step and ascertain whether or not they need further testing before going to a doctor.
Heck I do it all the time, as a matter of fact, my daughter was 4 years old the first time I ever took her to a doctor.. when the pediatrician came in, he was flabbergasted that any parent could make it four years without a doctor so he sat down with me for a while and asked what I did for fever and how I handled some of the more common situations any parent faces.
I answered each of his questions and each time he eas surprised that at every answer it was something he would have told a patient's parent to do, asked me where I learned all this medical knowledge.. was shocked when I told him my grandmother..
People need doctors much less often than they think they do.. for real. Certainly some situations require antibiotics and medical treatment, but far less than most people want to imagine.
(As a beside, I did get my kids vaccinated but did so at a free clinic so it never amounted to seeing a doctor. )