Looking at this invasion from a nuts and bolts perspective......
Successful military action, these days.... requires good intelligence and a co-ordinated approach with air, mechanized, and infantry assets, good lines of communication, and a strong logistical tail (food, ammo, fuel, etc)
The Russians have a huge advantage over Ukraine in terms of numbers of forces and equipment, but their offensive has shown a striking lack of cohesion.
Massive convoys have run out of fuel and Russian tanks and trucks have broken down along Ukrainian highways, creating traffic jams of sitting ducks. The infantry has not been fully utilized to protect these columns, these convoys firing off missiles and rockets seem to take up the bulk of their activity.
More and more stories are coming out about the infantry, with a lot of these 18-19 year old conscripts, who are facing veteran Ukrainian units (border fighting), without motivation, direction and supports (shades of Afghanistan), with predictable effects on their morale. There are even (unconfirmed) reports of some units handing over their weapons to the Ukrainians, and being allowed to just walk away
Russian air power has been mysteriously inert, so far, Ukrainian air defences have not been suppressed, yet (huge surprise)
Their vaunted electronic warfare asserts, have not been in evidence, either - Ukrainian Internet is still up, and communication links in-country and beyond seem to be still intact.
Russians are losing the propaganda war, bigly.....those videos of confused and despondent Russian prisoners are a absolute ten strike in that regard. Overall, Putin's attempts to discredit Zelensky and NATO unity, have backfired in a spectacular manner.
One gets the feeling that Putin ordered this invasion, somewhat off the cuff, blindsiding some of his generals, and certainly a lot of his troops. He was expecting a quick victory, while other countries talked about what they might do - the quick closing of ranks with NATO and the rapid response with the sanctions, etc...has come as another nasty surprise. This offensive is costing Russia around 10-15 Billion per day, to go along with the tanking of the stock markets and rouble
Sure, the Russians have the military muscle to smash through, and take Kiev, and perhaps put a sock puppet in there and call him President. But to what end? Insurgent warfare with 40M Ukrainians? A uber larger version of Afghanistan?