Larry - I completely agree with your assertion that there has been a breakdown in the consensus about what constitutes "important" jazz. But I think it began well before the 1990s.
I would argue that the end of the 1960s represent the end of consensus. Recent Mosaic sets that collect Joe Henderson's and Freddie Hubbard's Blue Note recordings from the 1960s appeal to nearly everyone on the board. (Whether they choose to buy them or not typically has more to do with duplication of albums that are already in their collection.)
OTOH, if we take those same two artists in the 1970s, there would NOT be the same sort of consensus among board members. I, for one, happen to love Joe Hen's Milestone stuff and Freddie's CTI stuff from the 1970s -- but I'd bet a dollar on a dime that there are plenty of board members who have no interest in it.
This is why it makes more sense for Mosaic to stick with recordings that pre-date the explosive diversification that took place in jazz during the 1970s.
Or at least that's my hunch.