They’re besieging it, allowing the Ukrainians to expend a ridiculous amount of resources (a battalion a day) holding onto it. The question is why is the Zelensky regime so desperate to keep it? Because once it goes they will have no chance at retaking the Donbas.
When in the history of war has attacking a city cost fewer casualties that holding it?
This war is much clearer if you know anything about military history and tactics.