Night Rider, you appear unwilling to accept that any pilot, no matter how experienced in the practicalities of flying, can ever be "professional" if he/she has not taken certain exams. Such a pilot is, you say “not really a proper commercial pilot”. Perhaps he/she does not want to be.
I do not suggest that flying a lot is in itself an indication of safety or competence, but suggest that it is equally artificial to equate the passing of exams with quality as either pilot or instructor. If experience will not save you from piling into a mountainside, will exams?
I don’t think that I was making a point about my instructor who now flies 737s other than that he was a good instructor. I referred to him in order to make it clear that I was not having a go at hour-builders whilst singing the praises of gnarled folk-hero instructors. The bloke I referred to was a very good example of the great many who make a contribution to GA whilst en route to an airline job.
Re your barrister analogy, I know several very successful barristers who entered the profession other than through the conventional university route. This does not make them unqualified or “unprofessional”. They couldn’t practice unless the profession’s regulator allowed them to, just as no one can teach flying without satisfying the regulator that they are up to the job, and renewing their rating on a regular basis.
So, why such a downer on the (really rather few) Sunday afternooners who are legally qualified and rated to instruct? They aren’t competing with the majority of instructors, and the notion of a wave of blithering grandads stealing the crumbs from the “professionals” is I would suggest, exaggerated.