Ukraine is piss poor compared to Russia. For years Russia provided Ukraine with underpriced gas while Ukraine’s export prices increased rapidly, but due to the dysfunctional governments they had, they never were able to take advantage of that. Ukraine historically was an agrarian economy that was industrialized with the usual Soviet brutality, accompanied by agriculture collectivization and the usual mass repression. After the fall of the Soviet Union, it inherited a relatively good infrastructure and capital stocks, especially in energy, but it mostly failed to maintain that. Add to that the fact that since 1992, there was only one year when Ukraine had a balanced budget. There was a lot of growth in the aughts due to the high price of metallurgical during this decade, but Ukraine was mostly taking advantage of their existing industrial infrastructure inherited from the Soviets and failed to diversify and sophisticate their economy.

Besides, if the idea is to invade the country to incorporate some separatist regions, it doesn't make sense to destroy its economic basis and end up with a huge refugee problem and a completely deserted land you just conquered.

This is basically propaganda for gullible Americans that never traveled to Eastern Europe.