We are approaching that critical 4 week point where Ukraine's general mobilization is going to start to be able to show some real teeth. Kiev and Kharkiv have still not been encircled fully and are still being supplied. Mariople is cut off, but has not fallen and is bogging down the bulk of the Russian invasion. Odessa has not been engaged at all, preventing Russian forces in Transnistria from effectively participating.
With lethal western munitions now pouring into the country and the loss, by most estimates, of around 1,000 supply vehicles, the Russian Army now has about another 4 weeks to break the sieges of Mariople and Kharkiv. Kiev is not as important as those two battles. If they can get Mariople and Kharkiv they can roll on and seize the Russian side of Dneiper and declare victory. I think Odessa is completely out of the equation at this point, so Ukraine is not going to become landlocked. I don't think the Russians can take Kiev either at this point. All they can do is keep Ukraines best units pinned down there and out of the Eastern Theater.
If Mariople does not fall in the next 4 weeks, Kharkiv is not going to fall, because the Russians cannot cut off Kharkiv until the Southern Front is secure and those forces can turn to the north and cut off Kharkivs resupply route. Worse, at this juncture Russia's supply train will have become exhausted while the Ukrainians will remain fully supplied. To continue the war, Russia will HAVE to declare a general mobilization, call up its reserves and institute the draft. Something that may be politically untenable for Putin.