WRT to the concept of "modern armies", I think that is relative. The Soviets - err, Russians, or at least Putin - still seem to be wedded to the concept of grinding down their enemy by sheer preponderance of force - Putin doesn't care how many Ukrainians or Russians he kills to meet his goals. The Ukrainians are at this point in the war fighting a high-level, high-intensity insurgency, and are being essentially reactive (with help from the West as noted). NATO countries would be much more economical of their human capital and rely even more on technology and advanced weaponry. Does that make them more "modern"? I would argue it is more the nature of the war as it is being prosecuted now as opposed to any concept of modernity.