But Japan experienced that change already and it wasn't apocalyptic by any means. Puranjay's claim here is almost literally "change will happen, and it will bring grief." So change happening without much grief runs right against that.

Meanwhile, the US has had any number of highly-adversarial, occasionally-violent political fights in the last decade while still in that "grow the top line" mindset.

You could make a plausible argument that those additional few decades of "growth" has a lot to do with the violence and unrest, even, not the other way around. (For instance, see any of a number of takes from all over the political spectrum blaming increasing stratification of elites.)

Hell, wasn't Marx predicting internal upheaval and self-defeat of capitalist economies many, many decades ago based on the same sort of demographics/populations/resources economic arguments? Things will change is an easy prediction, they haven't ever been stable. But it's also a meaningless one if you can't convincingly show that it's this decade not "any time between 10 and 200 years from now."