I suspect that "decadence" as a social analysis is more appropriate to the history of tributory social orders based on the appropriation of use values from a peasantry. (Actually, Adam Smith, though he does not to my memory use the word, offers suggestive observations re European feudalism as to the grounds of such "decadence" in tributary societies.)
But in any case, I think the provisional explnation for this "relentless trivialising" is that, for about 20+ years there have been no *significant* differences within the U.S. ruling class that would provide the grounds for a politics of issues -- hence the politics of trivia. The WSJ has been leading the chorus to get Clinton on moral grounds, but in reality the differences in principle between Clinton (and the whole leadership of the Dem.) and the WSJ range from paper thin to zero.
If a crisis of the magnitude Mark suggests (or even a much lesser but global crisis) does develop, differing perspectives on how to confront that crisis will generate serious divisions within the ruling class(es), both within nations and between nations, and the debate over those divisions will quickly replace hassles over stained dresses.
Though from our perspective the New Deal may have been the dedicated servant of rather than treason to capital, many sectors within the U.S. ruling class *really* believed that Roosevelt was a "traitor to his class." There were more important things than symptoms of "decadence" to occupy that class and the press lords within it.
Carrol