I'm most grateful to you gentlemen for the stimulating insights you've provided on this topic - and you've enabled me to reconsider my main proposition more incisively.
I'm content to stand by the proposition that there is - generally speaking - a world of difference between the amateur and the professional, in terms of mentality and activity. Common everyday experience furnishes abundant evidence of this difference. And yes of course one can always find fringe cases and notable exceptions. When has human existence ever been a matter of black-and-white, cut-and-dried categories? (Well, perhaps Disney might want to take out a 'contract' on me for saying that, lolol.)
That said, I'd readily agree that we might be falling foul of usage of certain words and their meanings or connotations here. Let's see if I can tidy things up a bit.
Not all amateurs or hobbyists are dilettanti, and not all dilettanti are amateurs or hobbyists. I suppose much of what I've tried to set forth in this thread is just another instance of the ages-old complaints against dilettantism. Amateurs and hobbyists can, if they so choose, focus only on their own particular delights in music and music making, without bothering with any real commitment to the vast panoply of knowledge, craft and skills that adept composers typically strive to acquire, maintain and develop in their music endeavours. In this case they could rightly be described as dilettanti. And still yet it doesn't necessarily follow that composers who have huge amounts of knowledge and skills under their belt will be successful as composers - professionally or not.
But there's something else in that mental state we call "commitment". I'll call it "service". Do you seriously want and intend to be of service to others, the potential 'customers' or 'consumers' of your music? Or are you merely interested in pleasing and delighting yourself, perhaps aiming always only for "solitary intoxication"? Of course one must enjoy and appreciate one's own music first and foremost. But what if the dilettante has tastes and sensibilities not only not commonly shared among many others, but also broadly avoided, shunned or even reviled? In that case I'd want to encourage the dilettante just to enjoy himself and not worry about trying to make it a livelihood.
Yes there are talented innovators who step out beyond the norms, and whose innovative works - though perhaps not immediately accessible - attract and eventually entice many others to step beyond their accustomed norms to assimilate and ultimately 'naturalise' the innovations. On the other hand, there is that problematic minority who are simply incapable of ever seeing, hearing or feeling 'through' the senses, sensibilities and feelings of others, and who typically try to bluff and fake their way into appearing to be taking part in normal social intercourse. And how many times have we seen examples of the latter trying to pass themselves off as the former?
But tasteless nincompoops, talented innovators and narc fakers are largely outside the community I'm focused on here: specifically, hobbyists and amateurs who don't know that they haven't yet marshalled all of their potential internal resources and capabilities. Cultivating serious commitment to being - potentailly at some future time - of service to others, is, I contend, one of the simplest keys to unlocking much of the as yet untapped resources and capabilities within oneself. Following a firm commitment of that kind, the ambition and extra work involved in acquiring highest possible levels of relevant knowledge and skills, pretty much fall into place and into line as natural consequences.
Throughout the history of civilisation, countless numbers of people in all walks of life have made that transition. It's far from being a matter of knowing some sort of esoteric formula or "life-coaching" method. Nor is it a case of having to attend the 'right' university, academy or conservatory. In the broadest and most general terms, isn't it very similar to becoming an adult? And just because there's art involved, it's not something entirely unique and a special case way out there all on its own. Whether or not it is or will become your livelihood, your serious commitment to "service" is central to the world of difference I've tried to describe above. Let the dilettanti be as irresponsible and self-serving as they wish - that's their choice, and a choice that's not without its consequences.