The current battlelines are absolutely unacceptable to Moscow, given that Russian troops are advancing every day. The real question, it seems to me, is how many ordinary Ukrainians would agree to Putin's stated terms (all annexed oblasti and the various sovereignty concessions) to halt the war.
Putin annexed four Ukrainian oblasts: Under the Russian constitution they are now part of Russia, yet Putin does not fully control any of those regions. So *of course* the current frontline is completely unacceptable to Putin. The Ukrainian army is standing far inside Russia, as defined by Putin.
alas