How about if Britain and France had minded their own business? What did they care about Bosnia or Serbia? Without them, it would have stayed another in a long line of eastern European wars that would have been settled behind the scenes by shifting poor peasants from on monarchy to another while creating a few more Dukes and Duchesses. Once the western democracies got involved, the war needed to be fought to the end. None of the previous methods of 'solving' what were really inter-family spats could work in an open political system.
The fact remains that on all sides there were 20th Century armies with 20th century weapons lead by spoiled greedy aristocrats who's brains were frozen in a 16th century vision of war and politics. None had the intelligence to foresee what would happen and none had the courage to get out of the mess once they got into it.
With all the carnage, perhaps it was necessary cost to be paid for the destruction of monarchy.
"A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves money from the public treasure. From that moment on the majority always votes for the candidates promising the most money from the public treasury, with the result that a democracy always collapses over loose fiscal policy followed by a dictatorship. "- Alexander Tyler
Im a Monarchist so I don't take any joy in the destruction of Monarchy.