Aldavis, without taking exception to any of your observations I hate to isolate the form to that which existed in one narrow period of time and which if accepted as fact would then preclude having a mind set that would allow you to experience growth. To do otherwise would be to define what jazz is and when it died. Hell I could argue that Jazz died with Ellington....take your pick and name a composer/performer and a date and we can create a tombstone.
Review the history of classical music. I'm sure there are many folks who thought (and perhaps a few still do) that the death of the last 'romantic' composer precluded the introduction of anything meaningful. Then the music of the early modernists, now universally accepted, when accepted challenged succeeding componsers. Unfortunately they knew not how to take the form forward in a linear manner and went off in a totally different direction, producing atonal/dissonant music bereft of anything comprehensive to anyone other than a fellow composer or musicologist.
Neo-classicists and neo-romantics existed, wrote music, but could not get it played and were generally dismissed, by the 'experts'. The halls emptied and the classical format languished. From the 80's forward we have seen the emptiness of that time and have opened our minds to the music of not only neo-classicists and neo-romantics who are expanding on a form long established, but composers who are contemporary 'modernists' with something to say that is worth hearing (IMHO of course).
So while I would agree with you, to some degree, that we are certainly in a time where the music is so unlike what we grew up with and have learned to venerate, and it is fair to call it (smooth jazz) nothing more than elevator music, we should be careful not to close our mind to the possibility of the resurgence of a new form of 'jazz' should it be discovered and published/played or created by an unknown contemporary jazzist.
Anyway those are my thoughts on the subject. :-)