Well, well!
I can certainly think of one composer who's not terribly popular on your list!
I agree that there was more "paint by numbers" work in Stravinsky's later output. But then, there were more commissions, less time, and so on... That's not an excuse. But to be fair, and at the risk tremendous verbal assault, there was also certainly much done "by numbers" in Haydn, Mozart, Beethoven, and many other "great" composers as well, and for similar reasons. I mean, when composition is one's daily life, one has bad days!
I think he was more confused than anything by the attention [to his early works], since he didn't really see these pieces as being so incredibly inventive as people felt them to be, and this for the very reasons we're talking about them now; the massive debt they owe to Ravel and Debussy. I mean, Firebird basically IS Debussy. Petrouchka is brilliant, but primarily for it's formal/conceptual innovation - the orchestration is only a few steps away from Debussy. Only the Rite is singularly brilliant - both in orchestration and form/conception. Though it owes much to Debussy, it is clearly the work of another generation, and conveys a very clear message that "times have changed". However, all that aside, the works I find to be most "inspired" from that period are lesser known works like L'Histoire du Soldat, Les Noces, Renard, and Priboutki, all of which have an intense, soulful drive... They seem almost ancient, in spite of the fact that their language is clearly ahead of its time.
The other thing to consider is the fact that they were "early works". I mean, I've already found myself a little irritated when people close to me wonder why I don't write like I did a few years ago. But the fact is, there's nothing so unfulfilling as regurgitating the same language over and over. We all need to find something new to strive for in our music. If we lose that deep urge to push ourselves forward, we lose the very inspiration that makes our music worth listening to...
Finally, there certainly are numerous deeply inspired and emotionally powerful works in Stravinsky's post-Rite output: Symphonly of Psalms (a brilliant orchestration, as well), Concerto in D for violin and orchestra, Duo Concertante for violin and piano, the Mass, and many parts (though perhaps not all) of Canticum Sacrum, to name a few. To simply object to Neo-Classicism is not a particularly persuasive argument. Stopping to look around himself, Stravinsky very clearly saw that a whole way of speaking, a whole musical language was coming to an end - and he was thoroughly immersed in that language - so he responded. I think he responded brilliantly. You, among others, do not.