The Ukrainian army has gone from being one which surrendered its Crimean peninsula to Russia without firing a shot in 2014, to one of the best land forces on earth by 2022-2023. Its economy and cities are in ruins, but the Ukrainians are not anywhere near ready to quit. Simply holding back the Russian military has morphed into a scenario where the Ukrainians might be in a position to outright defeat Putin's legions & drive the from their soil.
Russia has been in many wars over the decades and centuries but has not really lost a conflict (excepting Afghanistan, where they - like so many other foreign invaders - simply got tired and quit) since World War One. Now, they may be on the cusp of another defeat. The Russian army simply cannot go on like this forever. Their 1917-like moment may not be too far off. The Wagner Group (a shadow army, more than anything) and the Russian army may come to blows. Desertion remains a constant problem. Draft evasion is commonplace. Alcoholism is growing worse, even by Russia's relaxed standards. Officers fear their own troops & those troops fear their own officers. ,The economic woes of the country worsen every day.
The last 15 months have proven that Ukraine will never, ever again surrender their independence to being a province of Greater Russia.
Ukrainians fight without pay for the cause of their nation merely existing. They lose, their country vanishes off the map.
Russians fight for money, or to get put of prison, or out of fear of not fighting. Not a recipe for success.
The death of the Soviet Union may not have been 1991 after all. It might be later this year.