WWI makes no sense (or perhaps, we understand it better) because over a hundred years have passed, and the highly emotive propaganda of the time no longer persuades us. If you were listening to your pastor thundering in the village church about (say) nurses in Belgium in 1914 you might not have had the emotional distance, or education in cold politics, to recognise that what was really going on was the death throes of the Austro-Hungarian empire and the fight for hegemony in the empires that remained. (Not to diminish the crimes in Belgium, btw, but they were part of a bigger picture that would have been hard to read in 1914.)