Anxiety isn't a plague of the 21st century, it's a fundamental aspect of the human condition.

We did not evolve on top of the food chain living in relative paradise, we evolved as prey animals who could be eaten by a bear at any moment (or another group, or just slip and break our legs and die).

Anxiety, even when everything seems ok, is the evolutionary response that has kept us alive. In previous centuries we still just had tons of stuff to blame our anxiety on, the main difference with now is just that so many people are living lives of such little hardship and yet are still anxious, that it's making everyone go 'now hol up a second, I think this might not be entirely rational', and it's not and never was. Anxiety is a natural emotional response / state that causes our logical brain to cast about looking for things to ascribe it to.