Errikos, once again you've helped me question, refocus, revise and clarify my mind on a topic at hand; I'm most grateful to you.
Unfortunately for any science or even philosophy on this topic, we're all up a gum tree - and I do mean everyone. It's still not known what music does to and for us as individuals, nor to and for our cultures. So how can we possibly know with clear and rational certainty how and why any particular composition or composer is more or less worthy than another? Well, though intractable to science, we're not dealing here with complete imponderables; we can and often do intuitively gauge the weight and worth of a composition or a composer.
Let's look back to a time long before universities taught everything and academic qualifications pretty much dictated what 'professional' services one should and shouldn't be trusted to provide for others. Hasn't there always been a 'Rubicon' in any earnest endeavour? For instance, we'd never confuse a child with a blacksmith, nor an archer with someone who just likes to throw sticks, nor a storyteller with someone who likes to sing a ditty now and then.
We naturally get to know the métier of particular individuals in our communities. And when it's known that a person's métier is backed, developed and maintained by their longstanding and serious commitment, devotion, fidelity and sacrifice, we're far more likely to avail ourselves of their services - we know the person has crossed the 'Rubicon' in their life. And of course word gets around. Today, perhaps this isn't as commonplace an intuitive matter of everyday experience and common sense as it used to be. Yet I believe the basics of this ages-old social and cultural phenomenon are still there, somewhere, in all of us.
The word "professional" can mean someone who makes a living in some particular endeavour; but also someone who has been professed into a faith, i.e. been received into a religious order under vows. So there is this communal or public dimension to the word "profess"; it involves more than simply what an individual is apt to aver. The Oxford English Dictionary gives the derivation of "profess" as from the Latin "profess-", meaning "declared publicly", from the verb "profiteri", from pro- "before" + fateri "confess".
Culturally speaking, it's long been a serious and even solemn matter to designate someone as a professional, reflecting the fact that the individual has been publicly acknowledged as having crossed the Rubicon in his or her life, having made a deliberate and all-encompassing commitment to a particular occupation.
The dilletante, by contrast, makes no such commitment to acquiring relevant knowledge and skills, nor to being of service to anyone. He crosses no Rubicon in his life, all options are still open and available - or so he likes to think. As I use the word, the dilettante can be seen as the very worst kind of amateur - irresponsible and wholly self-serving, and perhaps self-deluding, grandiose and antisocial too. In other words, he's the last type of person from whom society would expect or seek a worthy service. Their self-expression may not be linked in any meaningful way to society at large, perhaps instead arising from some abstruse intellectual constructs, ideals, or just plain old puerile wishful thinking. It seems unlikely to find dilettanti among those who've been through the academic mill in music; but I suppose it's possible, especially nowadays when universities seem to be making their (incredibly expensive) courses ever more comfortable, attractive, easy and fun for any and all students.
What's in the back of my mind here is the worry about today's ever increasing tendency to presume - with militant obstinacy - that one can be whatever one chooses to be, by simple act of will. History and all common sense is against such immature, irresponsible and antisocial nonsense; but that just seems to inspire the culprits to up the ante and double down on their preposterous schemes. JP Sears - with cruel comedic aplomb - hilariously parodies an example here: