NATO did not know its enemy in Ukraine.
When I was in officer school, pre-1991, NATO was less dependent on air-superiority than it is today. We also had some good air defense systems. Our artillery was not superior to the Soviet one but was well layered – from short, medium to long ranged systems – and would have created very significant damages. We also had good pioneer equipment that allowed for the crossing rivers and ditches as well as serious mine fields.
All this changed after the 1991 Gulf war in which U.S. air superiority and tank fist destroyed the Iraqi defense forces. That war was misconstrued as a big win when it in fact was simply the effect of a by far superior professional force over a unmotivated conscript army with old and often defunct weapons.
As an effect of the first Gulf war and later operations in Serbia, Afghanistan and again in Iraq the believe in NATO air-land doctrine was reinforced. Air superiority was the holy grail while the strong land force capabilities atrophied. An emphasis on guerilla suppression and on vehicles that could withstand simple improvised explosive devices (IEDs) in Iraq and Afghanistan further unbalanced the force.
It explains why the Ukrainian troops were miss-trained and miss-equipped for a counter-offensive even when the opposing force was a much harder to crack one than some goat herders from Helmand, Afghanistan.
I’m pretty sure NATO would also fail the other half of the equation too. And, at any rate, you don’t need to worry about Sun Tzu when you’ve already failed W. Edwards Deming 101.