I've found in my experience that (many, not all) self-proclaimed "experts" do tend to grossly overestimate the capabilities and competence, and will impede those who are more capable than them for fear that they will diminish the value of their "expert" status. I feel this article is correct in stating that the appropriate way to approach a problem is from the perspective of an amateur, as amateurs typically have little fear of abiding by rules that have congealed within the minds of the "experts", and are more willing to take the chance of being wrong when success is imminent.
As they say, "an expert is someone who has made the greatest possible number of mistakes in their field."
I remember reading about a study where people who are below average at a task tended to rate themselves as competent (or better than average) for that task, while more competent people wold under-rate themselves.
There are all sorts of possible explanations (don't know enough to know you suck, pride, etc) and I don't think the study really looked at causality at all, but yes, I think the phenomenon is well known.
The study you're thinking of is probably "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own
Incompetence Lead to Inflated Self-Assessments" - it's completely fascinating and slightly worrying.
I'd say that's true of some, perhaps a few self-proclaimed experts. Most people who claim to know something in a field actually do have useful knowledge to impart.
Sure, there are quack doctors and flim-flam car repair men and consultants full of bafflegab. But most doctors really do know something about medicine, most mechanics know how to fix cars, and most consultants have highly useful experience to share.
That's my experience with experts. Maybe I'm not smart enough to know how little experts really know?
As they say, "an expert is someone who has made the greatest possible number of mistakes in their field."