[Chainmail]

The "stationary" part is what infantry tries to avoid, unless they have run onto serious opposition and the offensive has stalled.

Modern maneuver warfare - which is what Russia's force is supposed to be tailored for - should be able to maneuver around opposition and attack from the flanks.

That they aren't, shows that they have hit something that is stopping them and they can't get around it.

[marcusmaximus]

Not only are the Russians stopped outside Kiev, they’re being encircled now in Bucha, Irpin and Hostomel. No supply lines. No escape.

[Dr. Franklin]

The "stationary" part is what infantry tries to avoid, unless they have run onto serious opposition and the offensive has stalled.
Modern maneuver warfare - which is what Russia's force is supposed to be tailored for - should be able to maneuver around opposition and attack from the flanks.
That they aren't, shows that they have hit something that is stopping them and they can't get around it.

Maneuver warfare requires the ability to move. It appears that the Ruskies had their supply lines cut, and they are stuck in places. They also appear to lack air supremacy. Things would then be reduced to more basic tactics favoring the Ukrainian, like WWI with trench warfare and more disciplined advances to avoid creating vulnerable salients.