I remember buying the premise when I first read it, in part because decadent societies that have forgotten their technology were such a common trope in the SF that I was reading at the time that it was easy to nod along with the premise without thinking about it very much.

Now, many years later, it's somewhat obvious to me that this trope is absurdly more common than any evidence of this effect in human history (yes, yes, ancient Greece, but still). Most writers have now shifted to some sort of apocalyptic explanation for their downfalls of civilization, but haven't abandoned the idea (I'm sure for the understandable reason that rediscovery of ancient technology is a fantastic story hook that I still haven't gotten tired of, despite its implausibility).