In all honesty, if Russian forces had used normal Soviet doctrine for bombardment and destruction of airfields and military strongpoints, they could have. They assumed most of the Ukrainians would welcome them in and they could get to Kiev fast.
But the period of time preparing for the attack and the false perception of their reception really messed up their timeline.
I also think that we are seeing the obsolescence of tanks. Modern anti-tank weapons are just too effective. Sure, there's always been Panzerfausts and Bazookas but they weren't nearly as destructive as a modern FGM-148 Javelin, soon to be littered all over the grounds of Ukraine and finding their way into the hands of God only knows. This weapon is a game-changer.
Russia did not have a large enough force for an invasion nor did it have a big enough logistical tail to supply the force they did have. The invade needs 2x-4x the force the defender has because as he advances he needs to occupy and control the territory he is traveling over. He also needs to bring all his sh*t with him. The defender doesn’t need to bring his stuff. He already has it and every mile of road or rail or river the invader travels over becomes his to maintain adding even more logistical woes. Then at the point of the spear the invader needs more men and guns and maneuverability than the defender as well. The longer operations go on, particularly in a large country with bad roads, poor climate, and a lot of rivers, bridges, lakes, and bogs the tougher things get. While I still think the Russians will win I would not bet heavily on it. Putin should probably have consulted the ghost of Charles XII before invading Ukraine.