It's isn't Ukraine in isolation, it's Ukraine being propped up with an enormous amount of logistical, financial, materiel, intelligence, and technical support from most of Europe and beyond.
Without that Ukraine would have collapsed in weeks even considering the amateurish misadventures of the Russian military.
The reality is not so much Ukraine comfortably holding off Russia as it is Russia still managing to prosecute a war against most of the rest of the Democratic world, only it's taking place entirely in Ukraine and it's overwhelmingly Ukrainian lives paying the price.
Once this is resolved, all Russia has to do to completely destroy NATO as a going concern is snip off and hold a small part of Estonia or Latvia, and then they'll be free to do the same to practically any other European Nation near their border as they have to Ukraine, only chances are that nation, Finland for example, is going to be far less able to resist Russian aggression simply because it's nowhere near the size of Ukraine and poses nothing like the same logistical issues.
This is why it's of utmost importance to ensure Russia loses this current fight. It isn't just about protecting Ukraine, it's also about diminishing Putin to the point whereby even his own supporters lose confidence and would not countenance another military misadventure.