As a counterpoint to this entire line of thought, I'd recommend reading "The Fremen Mirage", a series of blog posts linked to below. It does a fantastic job of going through the history of the idea of "decadence" as what destroys society, and of the idea of "hard times" as the crucible to form strong fighters. The long and the short of it is that there is no historical evidence for this idea, that the "decadent" groups had massive advantages over everyone else, and that the original idea of "decadence" tended to be created for internal political reasons, rather than any true comparison with outside groups.
https://acoup.blog/2020/01/17/collections-the-fremen-mirage-...
(My description is summarizing to the point of uselessness, and I highly, highly recommend reading the series.)