Overall, an aggressor has to "find, fix, and finish" the enemy to complete the kill chain. My understanding is that the general idea is to invest in platforms can move quickly, continue to decentralize command, and adopt a new warfare doctrine for the "pacing threat" in the Pacific. If you're interested in learning about contemporary doctrine--particularly in the Marine Corps--I'd suggest you look into EABO, which is the war-fighting doctrine that's being proposed for conflicts in the Pacific.
Now that ATGMs are everywhere, armor is no longer invulnerable enough for this to be the main strategy - you need “combined arms operations” - infantry and air support to protect the armor. The Russians are not acting like this is the case, which is why their tanks are getting destroyed left and right.
Armored vehicles will never be obsolete - if you’re sending in infantry or artillery or whatever, it’s still better to have armor for eg. small arms fire and shrapnel - you just can’t rely on its strength as the core of your strategy.
tl;dr: the russians are demonstrating the failure of a particular strategy/theory on how to deploy and use armor, not a failure of the concept of armor itself.
In Georgia in 2008, skirmishes began in earnest on 8th August, and Russia were ready to roll into Tbilisi by the 14th.
I believe that Putin expected Ukraine to be very similar to Georgia - very fast advances to the capital, and ultimately capitulation from the Ukrainians to the Russians almost immediately.
The key to winning in Georgia was an overwhelming display of force. In Ukraine, I believe the strategy was the same - let Ukrainians see tank after tank after tank rolling through their villages, gently 'soften' the cities with artillery before rolling through the cities, and reach the capital in a few days. Furthermore, I think Putin genuinely wanted to avoid civilian and military casualties as much as possible, so a 'blitzkrieg' was preferable.
If you're moving that quickly, you don't need supply lines, you don't need logistics to the same extent, especially if your plan is not to occupy, just to withdraw after (for example) reinstating Yanukovic.
I think it's a legitimate strategy, but they gambled that they'd be able to achieve it and lost. That miscalculation has cost Russia a lot of time, morale, and equipment. I think now they're starting to adjust to the reality, which is that Ukraine were stronger than they were expecting in the first place, and on top of that, they're being supplied with weapons and real-time intelligence from the West. Assuming diplomatic efforts continue to fail, I see Russia now withdrawing to territory they are confident they control, and consolidating their forces, and beginning a war of attrition, which in the long run, Russia are likely to win.
However, there's a good chance that diplomacy will be successful. This war is incredibly costly for Russia, and if Putin finds a way to spin it that Russia have 'won' or 'achieved their objective' or whatever, then I think he will take that route - provided Russia maintains control of Sevastopol.
If the USMC ever finds themselves in the situation of having to storm the beaches of Hainan may God help them. But then the US nor China are dumb enough to get dragged into a fight like that.