There have been plenty of wars fought without people genociding citizens in their own country like Germany, or crazy techonological developments like nukes.
Humans have always been barbaric as hell in wars, but, WW2 was a new level, in a lot of ways.
Even WW1, the footage was very grainy and hard to find.
Footage of the Holocaust really showed just how disgusting humanity had become. Then Vietnam happened, and the footage from it proved that all of the bullshit about war being good for people was proven to be completely false. Modern war makes profit for the rich, and gives death and destruction to everyone else.