As long as Ukraine has manpads helicopters and low flying aircraft are always going to be vunerable.Even if it wasn't well planned, my critique of Russia is mostly about the state of its military
Aircraft are flying blind and then get shot down. Helicopters flying blind without cover. Formation convoys moving in Ukranian roads like they would move in parades in Moscow. Drones/air support is almost non-existent existent
Very few troops committed, only 50k (with 100 on reserve + rotated). They need 200k extra troops to make proper fronts and secure their supply lines
If Russia or China had been handing out modern manpads like candy to Iraqis and Afghans before America invaded, they'd have similar problems.
Deploying 200,000 into enemy territory would burn up a lot of food, water, fuel and so on. Deploying a small number forward and keeping the rest as rearguard keeps supply lines protected.
I've not seen any reason to believe that Russians had shortages of soldiers so far, whenever they've moved forward it's been fast.