Yes, what happens after all this money and political capital is invested in Ukraine and the Russians are still there? At what point does the US and NATO feel they must intervene with ground forces to save Ukraine? Just like Vietnam. The politicians can't let this end in a Russian victory when Zelensky starts asking for ground forces. An admission of failure. It also takes years of training to operate these weapons systems and tanks in combat situations. Does anyone really believe the US does not have advisors already in Ukraine operating much of this equipment? They are just going to send billions in weapons systems to people who are not trained to use them?
The Leopard 2 tanks are superior to the best Russian tanks. I don't think this is looking like an impeding stalemate. The Ukrainians have held their own with limited aid so far. Let's see what the summer brings before we start to make any conclusions about an unwinnable war.
For me, I don't see how Russia can hold Crimea this year. How can the prevent the Ukrainians cutting the Crimea Land Bridge to the north? Those Leopard 2's are going to be hard to stop. The Russian's couldn't stop the Ukrainians when all they had was inferior Soviet tanks. The Russians are now going to have more luck against the Leopard 2's?
How can they prevent the Ukrainians taking out the Crimea bridge itself to the east?
How can the Russian's supply Crimea from the sea when the Moskva could not defend itself?
How can the Russian's supply Crimea through the air when both sides have such good anti-aircraft defenses. The one strong point of old Soviet equipment. Along with lots of artillery.
How can any country hold territory that is cut off? Are the Russian's going to dig a tunnel from Russia to Crimea in the next few months?
So let's wait and see how the summer plays out for Russia.