Why does every generation think the next one is doomed?

You can predict how every generation will be perceived by taking a random annoying trait of adolescence and blowing it out of proportion. Boomers were considered spoiled brats, and Gen Xers were depressed teenagers. Likewise, Millenials are low-effort wannabes. Never mind the underlying mega-trend that what distinguishes humans is our neoteny, which is the enhancement of childlike features. For example, based on physical features such as skull shape, humans are almost literally chimpanzees who never leave adolescence.

Or never mind the underlying micro-trend that IQ rises every year based on the Flynn Effect. Or never mind that violence, based on deaths per 100,000, has been consistently going down for at least 2,000 years. And never mind that generational stereotypes are popularized by a news media that is primarily consumed by adults. Adults are always wringing their hands at their children. And so picking one common trope from a child development stage and applying it to a whole generation makes for a convenient, non-controversial stereotype.