Is it? It took a plague to launch a revolution in agriculture in Europe, leading to an increase in calories production, an expansion of human life span, and opening up an expansion in trade (which reflects an increased amount of consumption of goods beyond simple survival). The preceding periods of semi-stasis were ones of no expansion in human quality of life and punctured by the opposite when you happened to be in the wrong place during a struggle between elites.
In our concrete world: had Apple not been able to blow up the oligopoly where the phone carriers controlled what phones were available and what they could do, would we have the current explosion of software, tools, etc? In the US in particular the sclerotic phone oligopolies kept the mobile phone market at least a decade behind Europe and Japan.
This is exactly the issue I'm talking about. It's very plausible that the world got much better after the plague, and that the plague was an important catalyst. But it also seems obviously true that absolutely no one alive at the time would choose the plague in order to cause that improvement.
I think I agree with you about the Hayflick limit idea, but I also think it's useful to point out, as the parent does, that a sclerotic, moribund empire is probably a better place to live for the majority of people in it than not an empire, assuming there is trade and general stability.