What it did was end the concept of monarchies. Austria was ruled for 700 years by the Hapsburgs. Russia was ruled for 300 years by the Romanovs.
After the end of that concept (in which the rulers were somewhat restrained by the idea that God ruled above them),
we got the age of the dictators. There were no restraints on the semi-divine dictators — Mussolini, Hitler, Stalin, Mao, etc.
But each of these were confined to one country. After another great war, we might get a worldwide version — with no constraints on his power and demanding the adulation of all citizens...
It’s been traced back to the Congress of Vienna. If those people had respected national aspirations and drawn the borders along logical lines we could have been spared a century of abortive revolutions, the Franco-Prussian and subsequent world wards. Instead they tried to turn back the clock.
Italy kept its monarch - al the way up through WWII. The whole time Mussolini ruled, Italy had a king (that was when the Italian flag has a design with a cross in the center).