Imagine the roles were reversed, and somehow Ukraine managed to fully push back Russia, claimed a significant amount of land on the Russian border and was continuing to make very slow but steady advances all the while Russian forces seemed on the verge of collapsing due to manpower issues. And oh yeah Ukraine had up to something like 20 million more soldiers they could also mobilize into the war if necessary. Would you expect Ukraine to accept a ceasefire with no concessions besides Ukraine being 'allowed' to continue holding the land they already held, and only dejure at that, with Russia making completely clear its intent to rearm and reman?
This is not at all a effort genuinely intended to end the war. When you're at a disadvantage in war, ending it is going to require concessions that can be difficult to accept. The reason you make these concessions is because they'll be even more painful as your position further deteriorates.