This war has at least shown us that ;
Small and light infantry groups equipped with manpads and anti tank weapons were decimating entire enemies columns and supply convoys. (the most important ones) You can't win a war without effective logistics following your armies' advance on the ground.
More importantly the transparency afforded to communicate these serious problems up the CnC Ladder.
Lower tiers of Russian military plainly knew this....but it was not communicated to the higher echelons in any robust impactful manner to add as deterrence for this kind of campaign strategy they elected for.
A real morass of situation.