War isn't terrible. It certainly is not good, arguably bad. But it is not terrible. If it did not exist at all, life would not change much from 10,000 BC. Without any major conflicts, especially not a World War, we would not have Jets, Computers, Radios, Nuclear Energy (the best non-renewable source), and many other technologies. Now would be less futuristic than retrofuturistic.
There are also some benefits of not having a World War. Since imperialism was never defamed by the Germans and made difficult by the stress of bloodshed, the world is overall richer. Neither Africa nor southern/south-east Asia has a reputation of poverty as they are lead by the most powerful nations on Earth.
The people of these regions are still free as many (but not all) of these more powerful states are democratic, and will grant these regions some autonomy. The only reason there are so many nations today is because of things like the United Nations which exists as an anti-war measure after WW2.
When most people talk about a world without a WW1, they mostly think about the obvious, direct effects, but rarely the unexpected. What are some other consequences of a (relatively) Peaceful 20th Century?