Ukraine doesn’t necessarily need to retake its lost territories by force. They only need to keep bleeding Russia out until the war becomes untenable for them. Russia loses like 1500+ soldiers and 100+ vehicles per day, just to move a line on a map a few meters. Their economy is hitting double digit inflation despite a 21% interest rate. Their recruitment efforts are running dry and they may have to resort to mobilization soon to continue to fill their ranks with more cannon fodder.

At a certain point they may have to come to the negotiating table, and the longer this drags out the less favorable their position will be.