In the South, it did work out. They did manage to destroy Ukrainian BTGs around Kherson by direct assault in the first days and capture the whole South except Mariupol(which they had encircled) fully intact, including the largest NPP in Ukraine and bridges over Dnepr river. Kiev thing was mostly to force negotiations, but Kiev was too stubborn, so military now would focus in dealing with Ukraine Eastern army group.
in the south, fine. but it was clearly not war winning.
A successful attack that does not rely on the enemy simply giving up has to have the following stages:
1. preparatory: deploy forces to either achieve overwhelming superiority at a critical point, if the enemy can clearly see where the critical point is, or deploy forces to confuse the enemy regarding where the key objectives are, if there are multiple possible critical points. The russians did this. they clearly deployed their forces to confuse the ukrainians regarding how many and where the thrusts will be in the few days before the actual attack into ukraine proper.
2. break through: the initial assault force probe the enemy defences, identify weak points, the assaults force isolate or bypass strong points, open up the rear or interior of the enemy territory: the russians seems to have been more successful in the south than in the north, in the south they have invested a number of cities that functioned as defensive strong points. in the north they are stuck before kyiv. But no where have they actually broken through and opened up the rear or the interior of Ukraine. If anything, forces that should constitute the operational reserve used to exploit the breakthrough is being committed to try harder to achieve the breakthrough.
3. exploitation: having put neutralized enemy defences behind the tip of the break through advance, reserves are then committed to run around behind enemy lines, preventing the enemy from moving troops on strategic level. this is the war winning stage. I think no where has the russians attained this stage or are close to attaining this stage. even worse it also seems there is no more reserve on hand to take advantage of any opportunity of a break though should that happen now.
This does not mean the russians have lost. During WWII the germans were exceptionally adept at seemingly having shot their wad, and then skillfully scrap up reserves by retreating from exposed positions and ruthlessly breaking up tired and under strength units to aggregate them into a new reserve that then suddenly attack out of nowhere at the amazement of their enemies and retrieve the situation. The russians can do the same. But to be able to retrieve the situation, russia needs to create a new reserve so they can exploit any break through. this they appear to be doing by straightening the front line near kyiv and this freeing up troops for a potential break through elsewhere.
Would that be enough? Hard to say. we have to see.