Even earlier than that. "Pseudonymity" (not using your real name online) were adopted very early on Internet. Facebook is the big exception.

This first claim seems weak to me, and the arguments made in TFA are generally weak IMO. It feels that this theory tries to "eat more than it can chew"; they try to explain a lot of things with a single hypothesis, which in the end yields unconvincing explanations.

For instance, let me answer the 4 opening questions:

Why is the news media so interested in telling you how much the world sucks all the time?

Because fear sells; but that aside, one can also say that we are a species who loves solving problems, and pointing them is generally the first step to a solution.

Why are so many of us obsessed with distraction and managing our attention?

Because something is aggressively trying to steal attention - that is, actually, time - from us. It's self-defence at this point.

Why is it so hard to stop comparing ourselves to others?

Because of the atavistic instinct of reproduction, in which mating partners are selected mainly based on social status. It takes training to go against this instinct, and it is even more difficult when your time is being stolen.

And why does everything in art and design seem the same these days?

That's something a boomer could say... Mainstream designs can, maybe, look similar because when you target a large market you design for the average taste. Non-mainstream designs are just more expensive, harder to find, and less visible.