Not necessarily.
There may be some kind of negotiated settlement that avoids just how awful the Theory of Versailles was.
And with the U.S. keeping its powder dry, so to speak, we don’t delay entering a future war such as WWII which we really need to enter sooner.
There's always that hope.
However, (and this may be my cynicism seeping in) I think that a longer war w/o the United States would affect each side in very specific ways but which will ultimately cause them to double down. For the Hapsburgs they might be able to last a little longer than OTL especially with a Germany that is willing to prop them up even more than OTL thanks to a lack of American pressure exerting itself on them. Furthermore, as much as I detest Wilson, his wild idealistic ramblings probably caused the war to end sooner because the Germans believed they would only have to give up Alsace-Lorraine and keep the rest of their Germany Majority lands in Europe, maybe they could even join together with Austria and come off the war a stronger nation than they did coming in!
But with the way things are w/o the US as a belligerent, the allies will be even harsher (yes
harsher) than they were IOTL. Because they'll know that their victory came very narrowly and at great cost, the allies will be even more hungry for German blood than they were IOTL, and without the US to be a partner to the British in terms of meting out a lenient peace based on national borders to the defeated powers you might see a breakup of the German Empire in Europe. Possibly splitting off Bavaria and adding it to German Austria.
Regardless of which form it takes, the victorious Entente is
not going to be more lenient than it was IOTL, every factor present in this scenario goes against such a thing and the Germans will know this and because the Ludendorff-Hindenburg dictatorship's plans for victory usually depended on doubling down and gambling, they might stupidly decide to continue to hold out, believing that if they can keep forcing the allies into more and more costly (but successful) offensives that they will eventually moderate their peace terms and come to a reasonable settlement.