The underlying strategy is so sound that Russia now effectively owns 20% of what used to be Ukraine, ground which is never going back. Their military has gained extremely valuable experience in fighting a modern war. Additionally, European economy has been decimated and the second order effects (weapon proliferation, criminal syndicates, immigration, societal effects) are yet to play out.
Throw in the ever-present threat of small-yield tactical nuclear weapons being used by Russia if it ever thinks it's in danger of losing and I fail to see the logic behind all of this. Unless of course weakening Europe, utterly destroying Ukraine and strengthening Russia was the point from the get-go. Or you just need to admit that the US fucked this one up badly (as it has almost every other war it's been involved in over the last 40 years).