So let me get this straight: the authors of this study find that adults are showing signs of infantilism. And rather than looking at what are the consequences, they focus on the causes, and label the child - adolescent - adult stages as...traditional, hinting that it's just one of many ways in which we can "stratify" lifespans, so to say.
In fact, in the very first sentence, they say that this view is no longer relevant. As in, for who knows how long, it was. Suddenly it isn't.
This framework for viewing ways of organizing society as equally valid and inconsequential defeats the purpose of what, I believe, social sciences are for. I don't need a taxonomy of options, I want actionable insights!