The factors in World War 2 were much different, public sentiment didn’t matter. Nazis would have taken Poland in 1939 and pursue the Soviet Union sooner, it was inevitably a World War. World War 1 was editable.

World War 1 was very much avoidable. Time and time again World War 1 has been called unnecessary because the original dispute that triggered the conflict was limited.

There were people who foresaw, if not perfectly, how bad WWI would be, and tried to stop it. Many of them were socialists - Rosa Luxemburg and Karl Liebknecht in Germany, Jean Jaurès in France for example - and their final hope was that the proletariat of the European nations would not fight against one another, but we know how that turned out.

The problem was that there were not enough who were afraid, and that goes for WWII too.

There is also the view, which I think has considerable merit, which regards WWII in Europe as a continuation of WWI, and the Pacific war as a largely separate, though concurrent, event.