A.C. Douglas points us to this piece.
Was Mozart a transcendent genius, receiving his inspiration from some great unknown? I don't think so? Look at Mozart's operas, which seem to be the most frequently identified acts of brilliance. Die Entführung aus dem Serail is, at first blush, a very nice singspiel - albeit a bit heavy on the Turkish stuff. It is, in effect, the 18th century equivalent of musical theater. The libretto falls far short of the Da Ponte operas. However, Mozart managed to take the idiom of the singspiel and innovate with some really brilliant moments. He took existing media and improved them. The same, albeit somewhat more metaphysical material, goes for Die Zauberflöte. It is good fun, and it has some really novel and startling innovations.
However, on a dour note, how many of Mozart's operas are regularly programmed and recorded? 6, maybe 7. His later output, i.e., Le nozze di Figaro through Die Zauberflöte receive the bulk of the attention. How many of his symphonies are done regularly? How many of his innumerable chamber and solo compositions? Not bloody many. Mozart hovers like an eminence grise over the scene, but isn't all that involved. Was he a towering genius? Yes. However, was Wagner, Verdi, Bach, Beethoven, Mahler, or any of about ten others a towering genius? Yes. For every Die Zauberflöte, there is Il sogno di Scipione. Never heard of that one? Neither have I. It's K. 126 for you catalog nerds out there, and it was written when he was 18 or so.
Mozart's fame rests on a few dozen brilliant and innovative works. Just like everyone else. He wasn't getting the scores from nowhere. He knew what he was doing, but we seem to attribute all manner of magical mysticism to "what he was doing." Was he a great creator? Absolutely. Is his oeuvre a pillar of gold, unblemished and perfect? No. He was, as his death indicates, merely human.