I actually see it as a deliberate attention to stifle the creative flowering of the music and bring attention back to what the labels may have seen as more marketable music. By then the progressive aspects of jazz of the sixties was now to conservative listeners and perhaps many A&R people the outer edge, they didn't want to market music that went further, and musicians were going further. This didn't stop the music from evolving but it did impact the economics of musicians wishing to be even more forward moving. In a way this didn't/doesn't upset me that much as I too find that jazz up to the New Thing is my cup of tea, and further fusions and developments don't necessarily attract me.
Anyway as far as the Marsalises go I like some of their music, I won't lie, and I just don't read what they say, which is designed to get them attention I'd rather not give them, and much of what they say I just don't agree with and there is so much I don't agree with in this world of ours that I limit my exposure if I can.