I don't quite follow you in your assessment of Russia still being an 18th century empire, searching a circle of vassal states around it.Your economic assessment is spot on for a Western European or North American. However, I do not believe they think like that at all. Russia is an 18th century empire, for a time disguised as a proletarian utopia, that thinks in terms of vassal states. It is hardly just my assessment that Ukraine would have been dismembered and everything east of the Dnieper and all of the Black Sea coast would have been incorporated into that empire. A rump state with relatively few of those resources worth trading for would have been left.
I do believe paranoia with respect to NATO membership did play a part in the decision process. Obviously, that strategic goal has somewhat boomeranged with a new Finnish NATO frontier in marching distance of St. Petersburg that is already hosting surveillance assets virtually peering into ports of Russia's Northern Fleet - particularly those submarine bases.
I agree that we would not have seen Russian columns attempting to penetrate the Polish and Romanian borders. But I am equally certain we would have seen destabilization efforts across the Balkans fueled by their success in Ukraine.
In my encounters with Eastern European and Russian peoples, when they do express themselves clearly, they tend to mean exactly what they say. Putin for years stated: no further NATO expansion towards the east. Russian access to the Black Sea through the Sevastopol maritime base needs to be guaranteed.
It has all boomeranged in a spectacular fashion for them for sure.
I remain convinced that the West should rather seek an acceptable compromise agreement between parties, than letting this conflict run for longer. Sure Russia will weaken further, but is that truly in the West's interest? I'd rather have the Russia from 5 years ago, still incapable of confronting NATO, but at least giving China pause when they will focus their attention towards Siberia. In the mean time an entire country and an entire generation of Ukrainians gets thrown into the grinder.
There is no additional positive position to gain from having this conflict run any longer than it already has.