I don't believe the proper narrative about how the decline of the Roman empire was due to decadence. I believe it was a victim of its own success. Roman ideas, organization, and commerce spread out to the surrounding kingdoms, eventually each region developed a polity progressively capable of challenging Rome. It didn't happen all at once, and if you look at it in the micro, it does look like a decline, but in the macro, the so-called decline of the Roman empire was a story of progress.
You can generalize this. Isolate the idea that the organization was built on, then see what happened to it. Usually, you'll see that the 'killer app' that gave them the ability to rise to the top created a new world in which everyone has that ability to exercise it. If you don't come up with a new one, you'll eventually lose your privileged position.
There's nothing wrong with this at all. We just are wired to want success so we go looking for personal failures rather than thinking bigger.
Except you don't see this in the Roman Empire. If anything, the economic sophistication of their european opponents steadily declined, making war a more appealing option than trade for them.
And in warfare itself, with the exception of the Sassanids and the civil wars, the Romans did not face armies that had adapted their tactics. Rather, the longstanding issue of inferior roman cavalry in both quantitative and qualitative terms and the decline in quality of their infantry legions/ reliance on auxiliaries made them far more vulnerable to concentrations of heavy cavalry, horse archers, and non-pitched battles. For a variety of factors the averagesquality of western Roman armament and training consistently declined from about 200 AD on, which is the opposite of what you're saying.
Decadence is a politically loaded and over-determined word and there are myriad factors contributing to the fall of the Roman empire in the west, but the thesis that the germanic, central asian and gaulic tribes had successfully adopted Roman administrative and logistical forms has no historical basis. I get that it's supposed to be a cute metaphor for tech companies and market-wide adoption of an innovation, but if a metaphor is advancing a novel thesis that's empirically false, it's not a good metaphor.
You can generalize this. Isolate the idea that the organization was built on, then see what happened to it. Usually, you'll see that the 'killer app' that gave them the ability to rise to the top created a new world in which everyone has that ability to exercise it. If you don't come up with a new one, you'll eventually lose your privileged position.
There's nothing wrong with this at all. We just are wired to want success so we go looking for personal failures rather than thinking bigger.