>> In fact we do know how good doctors and lawyers are at their jobs, and the answer is "not very." Medical negligence claims are a huge problem. Claims agains lawyers are harder to win - for obvious reasons - but there is plenty of evidence that lawyers cannot be presumed competent.

This paragraph makes little sense. A negligence claim is based on a deviation from some reasonable standard, which is essentially a proxy for the level of care/service that most practitioners would apply in a given situation. If doctors were as regularly incompetent as you are trying to argue then the standard for negligence would be lower because the overall standard in the industry would reflect such incompetence. So the existence of negligence claims actually tells us little about how good a doctor is individually or how good doctors are as a group, just that there is a standard that their performance can be measured against.

I think most people would agree with you that medical negligence claims are a huge problem, but I think that most of those people would say the problem is that so many of these claims are frivolous rather than meritorious, resulting in doctors paying more for malpractice insurance than necessary and also resulting in doctors asking for unnecessarily burdensome additional testing with little diagnostic value so that they don’t get sued.

I won’t defend lawyers. They’re generally scum.