By having its whole identity hinge on being anti-Russia I mean the Ukrainian government, irrespective of the people who I'd say were neutral to positive on Russia in 2014, lukewarm to negative before the invasion and now negative for at least a generation. The purpose of the Ukrainian government, in the words of Adam Schiff, Lindsay Graham, John McCain, Victoria Nuland and so on is to fight Russia 'over there'.
No one except the Ukrainians cares about the Ukrainian economy. Putin is not scared of the potential of a backward shithole that hasn't moved positively in 8 years and makes even Russia look like Singapore, but by the military and it's the same thing the US cares about. 40 million people present a meaningful demography that an army can be built out of to border Russia, something that isn't the case for any other state bordering Russia right now. Crimea is the only warm water port Russia has and the only one with access to the Black Sea. It already went without water for 8 years after Ukraine dammed it in. A Ukrainian army, which as I was wrong about isn't actually a pushover, would eventually move to take down the separatist regions and Crimea and so seriously weaken Russia while penning it in to being unable to act even in its near abroad.