Every day the Ukrainians get stronger, with some of the best weapons in the world flooding into them, gratis. Every day the Russians get weaker, and spend their oil money rearming with old tech, at inflated prices.
The Russians are losing men. Had to scrap their age limits for recruitment. Whereas the Ukraine devoted all but the youngest and oldest men to the fight from the beginning. Millions, who have a reason to fight, and who every day are better trained and more experienced. Home court advantage.
Historical analogue: The British kicked American ass for 5 years beginning in 1775, and captured American cities. World commodity prices rose. Plainly, it was insane to fight against a superpower. The tide turned when another superpower (France) donated cash, weapons, and advisors to the Americans. Even then the war dragged on another 3 years
Putin may need a bigger mop…