The British, French, Italians, Romanians, and whomever else got sucked into the conflict would never have been able to cope with the German (and Austrian) strength freed up when the Russian war effort collapsed. Just as in WWII, in WWI most of the German manpower was in the east, and on all fronts the Germans had their adversaries outgunned. The only thing that prevented a Central Powers victory was the American Expeditionary Force.
That’s how I read it, but we’ll never know.