I think it means, to quote Depeche Mode, that “people are people”. I am often amazed at how each generation forgets or just doesn’t look backward to see that a lot of the problems societies face are in fact the same things they have been facing for quite some time.

Example?
Think that reality TV is morally questionable? Well, the Romans didn’t have TV, but they had reality TV. They just used lions and gladiators instead.

I think it is a trick of the mind. Sort of like if our brains were able to really comprehend that sex leads to children and all the responsibilites therein, we would die off as a species.

The mind has a fabulous capacity for reason and self delusion at the same time.