They have not done badly.
Got right through to the main city in less than two days, with, in the grand scheme (of troop numbers and equipment numbers they could use) , minute amount of damage to numbers of troops and equipment.
They go in with minimal troops and equipment, if they find a tough area (the airport yesterday) they go in properly with larger numbers and gain the area sucessfully.
They do not want to flatten everything, and kill everyone, that is not the aim here, if they did want to do that, they could easily have, without putting any troops into ukraine at all.