Russia has proven itself to lack expeditionary capabilities, by my reckoning, and that is all. Invading Russia would be an entirely different argument. It's funny, but the concern over their military might, in hindsight, was foreshadowing for what we're seeing right now.
i'll explain that^ by saying: In the west specifically here we've concerned over Russia since WWII. The 'threat' prompted all kinds of expenditures and development of weapons and wares, and because they were sold as 'capable'. Our entire defense mechanism is based on keeping the fight elsewhere. we are supremely expeditionary and we're really the only might on the planet capable of waging a war off our soil where the threat to defenders is real and present. We figured russia to be the same.. they are not the same. however, like N.Korea, if teh fight was brought to them they'd be an entire different nut to crack.... still not as tough as we though they were, but not a walk in the park either.
the corruption in the ranks of russia is apparent here too- the expenditures to support their military readiness was squandered. they're operational tempo on paper was and is unsustainable and unobtainable not due to piss poor planning or strategy, but based on material capability. it's not like they didn't spend the money to outfit the ranks, it's just little of that money actually went to that outfitting.... Chinese tires is the glaring example that caused all grades of grief and is the principle cause for a great big ass stuck convoy.
all that said- and adding that putin thought he was ready for such an adventure and being completely wrong (and because of lack of understanding actual readiness of his forces), there is another fold to this that everyone here needs to wrap their brain around- and that is the simple fact that information is being carefully controlled about this entire circumstance. there are parts in whole we have no clue about. the media is actively oppressing opposition to their narrative. before you think i'm being critical of Ukraine and giving russia an out, what i'm going to say contrary is "both sides are bad". just because there is one bad guy doesn't mean there aren't two and certainly doesn't mean there is a good guy. Ukraine is as corrupt a nation as there is- right up there with Russia, China, and US. when there is corruption present and on the scale it is, all bets are off when it comes to pointing out who is right and who is wrong. if you think you've obtained enough information to make a determination about that, and from the worldwide cabal of fake news peddlers, you're part of the pliable and moldable populace those in the seat of power want in a citizenry.