I think reaching Dnieppe river was and still is the real military objective of Russian forces currently operating in Ukraine, NOT taking the entirety of Ukraine.
I could argue that the reasons why Russia attacking cities is mainly to make the UAF in the cities to be pre-occupied and not giving them the slightest gap to redeploy those forces station at the city at their own flanks, so just mainly probing and "terror" attacks
From an earlier post:
I’m convinced that the Russians have no clue as to what they’re doing, now! Attacking cities when military commands, networks, installations, bases, and formations should have been the primary objectives, with individual units having (possessing) [edit] mission threatening capabilities, such as dispersed anti-air batteries being secondary. Whichever units holed-up in the cities could have been dealt with after the threats in the field were neutralized.
I could argue that the reasons why Russia attacking cities is mainly to make the UAF in the cities to be pre-occupied and not giving them the slightest gap to redeploy those forces station at the city at their own flanks, so just mainly probing and "terror" attacks