"There are so many composers that worked their lower intestines off for decades, but they couldn't hold the relatively lazy Rossini's or the 16-year old Mozart's-Mendelssohn's-Chopin's-Prokofiev's hats."
That is most certainly true, however, you left out the other two factors I have mentioned, and which I believe are as essential as hard work: cultivating and developing one's musical and general artistic sensibilities and, last but not least, fortunate circumstances. It is true one can work hard, but work hard on crap without even noticing and making no progress whatsoever, no matter how hard the work is. There probably would be plenty of examples to demonstrate that. However, I have all reasons to doubt that a composer who has constantly cultivated his/hers musical sensiblities and also had some additional luck to point his thinking and working procedures in the "right direction" won't, in combination with hard work, in the end produce results which will be both "inspired" and technically proficient beyond what I would call "very mediocre".
To sum the point up: your example above is certainly true in many cases. However, there are also innumerable cases where a long and hard road of development is seen before a composer reached and cultivated the sort of "inspiration" we admire in his music today. Among those who couldn't hold hats to 16-year old Mozart-Mendelssohn-Chopin-Prokofiev are, among others, 16-year old Beethoven, Schumann and Berlioz, or, for that matter, 30-year old Bruckner. However, all of the 16-year olds mentioned above combined together can't hold hats to 55-year old Berlioz of Les Troyens or 60-year old Bruckner of the 5th Symphony, or, for that matter, the 50-year old Draeseke of the 3rd Symphony or 55-year old Taneiev of the Piano Quintet. And that both in the "inspiration" as in the "technique" department. And that seems to me only possible if "talent" (which I grant probably exists variably in the sense of different "inborn" levels of a sort of elementary receptivness to music, both in the passive and in the active sense, but, and I would like to emphasise this, on a very elementary level) is not merely "moulded" by discipline and work, but actually developed and refined by all three factors (cultivating sensibilities, cultivating technique, and sometimes also having some luck). And this doesn't apply just to Bruckner, it applies, only on a different time scale, to Mozart as well. There is nothing in the works of 10-year or even 15-year old Mozart which necessarily suggests he will compose the A major Piano Concerto 15 or 10 years later.
"Everybody got the same instruction in orchestration at the Conservatoire de Paris in Ravel's time. However..."
However, not everybody developed and posessed the same amount of self-criticism, cultivated the same musical sensibilities, or worked on those as well on his technical proficiency with the same rigour and consistency.
"You admire sheer inspiration and talent because they are rare; not because they are the rewards of hard work."
I don't. Why should anything be admired merely because it is rare? Plague is fairly rare today, but I still have many inherent reasons not to find it to be a particularly admirable occurence. Rarity or abundance of something doesn't say anything about its inherent quality or worth. I suppose what you ment to say is that one admires sheer inspiration and talent because of they intrinsic qualities independent of hard work. On that I would agree in the same sense I would agree with your example of admiring the beauty of a woman (or, f.e. the beauty of nature) without necessarily having to admire her personal qualities and skills. However, I have no admiration or respect for either an artist for his "talent" or for a woman because of her beauty if all they had to do for it was to be born with it. Being born into something isn't either a skill or an achievement or a virtue. It is an accidental privilege (or accidental curse).
"Everyone is different of course, but I'd rather have composed that track than all the magically orchestrated animated films, all the fugati in Jaws, you get my drift..."
Ok, I suppose this example also sheds some light on our differences of opinion on this issue. I would, for all the reasons stated above, prefer to have composed the fugati in the Jaws...