Why can't everyone working in a given field be incompetent? When Dr. Semmelweis discovered that surgeons washing their hands drastically reduced patient mortali

Why can't everyone working in a given field be incompetent? When Dr. Semmelweis discovered that surgeons washing their hands drastically reduced patient mortality, he was dismissed and ridiculed. I would say that 100% of those surgeons were objectively bad at their jobs and therefore "incompetent" in a narrow sense. Groupthink can cause everyone in a given field to converge on the same orthodox belief, and if that belief is wrong or dangerous, shouldn't they all be considered incompetent? Even today there are many pseudo-scientific fields where literally none of the practioners are objectively able to accomplish what they claim... and it's not at all obvious that project management is not among them.