On the other hand, the best way to improve your capabilities is to use them frequently.

The Russian army assumed a state of readiness for the Ukraine invasion that turned out to be, well, less. Their special forces floundered, their logistics were (are still!?) unpalletized - using bespoke metal containers and wooden crates! Whereas the US military learned an awful lot from its (mis)adventures over the last decades.

I think Russia's strategy fault was more that they didn't expect the amount of support Ukraine could coalesce in such a short time.