That's a pretty fucking stupid take, our ancestors had to be busy all the time just to survive.
We are living in a time of 24/7 news and access to way too much information that's a way better explanation.
In fact I even like the explanation of anxiety being a result of abundance of calories more than this shit. That theory posits that our brains can go into overdrive simply because it has access to so many excess calories whereas in the past it didn't.
There is also the move towards white collar work, work that's not physically demanding, that we didn't evolve to deal with. Try going to the gym/exercising regularly and you will notice a significant drop in anxiety even on your worst days.