One other item I find fascinating is the lack of Russia to adapt to modern maneuver warfare. I think they actually believed that running around with t-72s and BTR 25mm auto cannons was going to just smash down Ukrainian infantry.
They completely underestimated drone intel, and modern atgms.
I saw a picture of a Ukrainian infantry platoon. Of about 20 people in the pic, all but 2 had heavy AT on thier back. Of those, they had 4 variants that I saw. Carl Gustav, javelin, panzerfaust, and an rpg-72 (I think it was a 72).