Interlocking alliances were the main problem. I don’t think most people wanted war, there was just no way to avoid it once it started.
It changed the world for all time. I doubt we will ever get over WWI.
Or Macho Grande. Those wounds run pretty deep.
Just before WWI, the World was globalized, one could travel from one part of the world to another freely, send money via wire without restriction. Metropolitan cities such as London or Paris boasted products from all over the world.
The entire generations born between 1880 and 1900 were wiped out.
After Belle Epoque, we got the horrors of modernity.
You are right, we never recovered. Totalitarian regimes (Communism, Fascism, Nazism) bankrolled by the oligarchs after WWI severely damaged us.
I think the other problem was that there really hadn’t been any great continental wars involving multiple powers in Europe of any scale or duration since Napoleon. In that time technology had advanced drastically, and I don’t think anyone really understood their newly built ability to kill en masse.
What would have then taken a generation could now wipe out a generation in a few short years. By the time they figured that out it had already happened, as inflexible old school war tactics got mowed down by the new technology at places like Yrpes and the Somme.