Just like software engineers are best qualified to evaluate software quality, doctors know medicine better than anyone else. Just because they are incentivized to protect their job doesn't mean they are wrong.
It was rather trivial for Boeing engineers to show, without a doubt, that the cheap offshored programmers didn't write software as good as they did. The design simply spoke for itself and didn't perform to spec.
Why not simply have doctors do the same? If their fellow medical workers can't deliver the same quality of care at the same speed and cost, then it should be trivial to show.
Doctors are at a greater disadvantage as there is not likely to be a sentinel event that kills 189 people at once. Nothing about the US medical system is trivial.
Consider the private equity run emergency department in the article, I am sure that they could make more profit off of NPs and that doctors wouldn't save private equity costs. The article suggests that NPs are saving private equity money while costing patients and taxpayers more. Speaking of quality, why should private equity care about quality if it doesn't effect their bottom line?