The problem was that the Entente never was willing to negotiate. Their war aims were such that they only could be implemented when the Central Powers were crushed. They had agreed not to undertake individual or separate peace talks, a pledge which Russia kept until her end. It took them several months to sort their war aims out between themselves for the peace treaties of 1919, no way this could have happened in any other scenario. - And on the German side the chance for a negotiated peace was also gone with the demise of Falkenhayn and the arrival of Hindenburg/Ludendorff.