Great point, although the DSM definition I quote from is explicit about how ordinary stresses aren't necessarily disordered. For instance, grieving the loss of a loved one may not be disordered.

But you're raising a deeper point, I think, about whether an entire society can be going off the rails. That calls for a philosophical or historical sense of mental health, and of the meaning of life itself, which is beyond the psychiatrist's purview. The psychiatrist merely presupposes the socially convenient answer to such a broad question.