The more important aspect was the social and government structures pre-WWI. Europe was still dominated by an aristocratic elite and a very class based society.

The more important aspect was the social and government structures pre-WWI. Europe was still dominated by an aristocratic elite and a very class based society. That elite drove public opinion and policy. It served as the officer corps. It served in government and in civil service. It's very difficult today to imagine a world so different from today, especially with regard to class. Ultimately what all that meant was that the bad old ways that European aristocracy had always worked continued apace. Empire was an extension of national pride, and primarily extractive and selfish. Foreign policy was also selfish and dominated not by the thought of maintaining order by by the idea of gaining advantage. And only moderated by the fear of a foreign hegemon and the desire to team up to prevent such in order to maintain the conditions that allowed everyone to scuttle about and get up to geopolitical hijinx for the benefit of their own country. These patterns of behavior had led to a great number of wars in Europe's past, it was a strong pattern. Wars fought for territorial or trade advantage: Wars fought to reign in a hegemon. Etc. That was how things were, even going back to the hundred years war and earlier. In the 19th century you had the Napoleonic wars, the wars of German/Italian unification, various imperial skirmishes, the Franco-Prussian war, etc. The point being, wars were seen as being an opportunity for advantage and positive change. And the powerful elite at the time very much had a fascination and lust for war due to its glorification as well as the immediate financial gain of being an officer. The concept of an existential war, the concept of wars that took millions of lives, the concept of a war where bullets and bombs were putting troops on the front lines in danger of death every day for years was not a concept Europe at the time could understand. And in the shock of the war a lot of the old ways of Europe broke apart and were destroyed. Post WWI Europe was much different than it was before the war, and you can see this culturally. Post WWI cultural artifacts tend to seem much more modern and tend to more easily resonate with modern sensibilities than pre-war stuff does. The point being, it wasn't just the alliances and weapon buildup that brought about WWI. More than anything it was a culture that saw war as a tool for gaining advantage, a culture that tended to fall into a war between great powers at least once a generation. That sort of culture doesn't exist anymore in the great powers. Even in countries that see geopolitics as a realm for gaining selfish benefits generally there just aren't a lot of folks who are eager to go to war. At best there are folks who think that it's wise to go to war in order to take out an enemy that's a threat, but that's a very different proposition than the pre-WWI situation.