How to explain the military disaster of Putin's armies in Ukraine?

Here's what struck me as a good military explanation (found on Quora) by someone who seems to know what he's talking about but is only worth reading by someone who is immune to the alternative facts that Putin devotees' plant around.

«I spent a decade (late 70s to late 80s) as a russian analyst and linguist. The Soviet Union had a massive army that dwarfed anything the West could put up. At least on paper. In truth, the maintenance required to maintain such a huge inventory of military equipment was prohibitively expensive without even taking into account the lack of discipline/motivation/training on the part of the maintenance crews. A significant percentage of the equipment was nonfunctional and many that were functional were marginally reliable. Not the best equipment to take into a rugged military environment. We have seen a repeat of this in the Ukranian campaign. The Ukrainians have proven themselves to be better at repairing captured russian equipment than the Russians are at maintaining them. What the Russians excel at is the complete lack of concern for the lives of their infantrymen (as shown during WW2 and the Ukranian war). To them, they are just cannon fodder. If they throw enough men into the fray, sooner or later they will break through. They have displayed this in both wars by using blockade brigades behind their troops. They do this to catch deserters as well as “encourage” the troops to obey semi-suicidal orders.

So in short, yes, overall (a few soldiers the exception) were and are inept. And overcome this by carelessly sacrificing their infantrymen.»  

Martin McQueen, Former Russian Analyst and Linguist at Federal Government of the United States (1977–1987)

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Postscript

"A new Afghanistan" says one comment. With a slight difference, I would say: in 21 years post-9/11 wars in Iraq, Afghanistan, and elsewhere, the U.S. and its allies have suffered about 15,000 deaths including contractors; in a year of war, Russia has had several hundred thousand dead. That is, in a twentieth of time, ten times more deaths.