It's true that a lot of the optimism around tech startups has waned over the past few years, and this trend has accelerated during 2020. Not just here on HN but in the U.S. more broadly.

I think a big piece of it is that current the crop of tech startups going public are largely unprofitable companies whose only "innovation" in many people's eyes has been skirting laws and foisting negative externalities on the broader public. These companies have also risen while the cities in which they are based (i.e. San Francisco) have deteriorated substantially.

All in all, the perception is that the current startup ecosystem isn't producing the same innovative, profitable companies that "lift all boats" the way it used to, and the increasing negativity and cynicism here likely reflects that.