It relies on a cliche of the idea of what an adult should be. But the premise that adults were more mature and not showing these traits before is flawed. Many 60+ years old strongly exhibits all the traits of the described "infantile personality" when their lifestyle and world vision is challenged, be it in their private or professional life. Sure if you judge by the capacity to masquerade and give the appearance of showing the traditional adult image of the older generation by definition the younger one will score worse. But it's a facade, on the inside the majority of older adults are still children.

> characterized by immature feelings (‘childish’ reactions, lack of willpower, lack of confidence), external locus of control (other people are blamed), inflated self-concept, low demands on self (accompanied by high demands on society), and egocentrism.

So you tell me none of your older neighbours will display this and instead be models of "emotional maturity (rationality, self-control, lack of impulsivity, etc.)" when you talk to them about lawn mowing, car usage/size, energy, meat eating, land use regulation, ...?

There is no more infantilism than before, what has changed is the definition of achievement.