decadent (n.): what less awesome civilizations say more awesome civilizations are; see also sour grapes.
Or, to be more precise, if you look up decadent in the dictionary, you will find that it has two senses:
- in a state of deterioration and decay, especially moral decline
- luxuriously self-indulgent
That human languages conflate sense 1 (bad) with sense 2 (awesome), they would say, tells you a lot of things about humanity, most of them uncomplimentary.