It is not as if Russia and Ukraine were two bitter enemies, locked in a death-match.
Ukraine is extremely close to Russia historically, culturally, etc, but they chose democracy, and were moving more and more toward a western style open and free society.
It seems that was too much for the Putin regime in Russia. Ukraine must now be brought back into the fold, and never again be allowed to stray.
Honestly, the relationship seems to be more like an abusive marriage than two independent states.
Is a peace treaty even really possible, or meaningful, with that underlying grievance? Perhaps only if Ukraine promises never to stray ever again, and to always be there when Putin demands it, etc. Or if Putin is brought to his knees with sanctions or other means.