Members of the tech community were never driving the decline in cousins or the population generally. Most of us here are wealthy and wealthy people tend of have fewer kids already. Even people here could reasonably have concerns about the future of the environment, our democracy, etc that might make having children seem unwise.
Most millennials, in fact most Americans, are not experiencing a period of abundance and prosperity. Their standard of living is in decline, their household debt is at record highs, and they still can't afford to buy the same groceries they normally would.
I think the better educated our species is thinking too much before having kids where as our parents and their ancestors kind of had kids and rolled with it. But even as a well earning tech guy, i can't help feel that being unemployed and being hit with one medical emergency can put my family on the street. In this time of abundance, i still feel like i'm being ground to dust by the man.