Stalingrad had an extensive sewer system that couldn't be destroyed that allowed infiltration and devolved into trench warfare once the Soviet lines stabilized. Keep in mind the Germans nearly capture the west bank in its entirety before they were driven back slowly.
Leveling what buildings you can does make it easier because instead of that 10 story building with 40 windows to worry about, you've now got some blown out building with maybe 4-5 good firing positions.
The Russians tried doing what you're saying with the 1st Battle of Grozny. They got massacred. The second time around, they just blew the piss out of it and drove off the Chechens. In terms of urban warfare, it is a lot easier to scope out ruins than it is to go room to room, window to window, house to house.
Seriously, a lot of this cliche comes directly from Monte Cassino and it is rooted in fallacy because there weren't even any germans up there to begin with. What you're basically saying is that HE is useless for removing an entrenched enemy, which actually runs counter to all doctrine.
If you can nuke it from orbit, you will. Then roll in and mop up the disoriented and dying.
An enemy that can simply run back into the rubble and take up a firing position doesn't say anything about your ability to remove their firing position via firepower. It means you're too weak to consolidate the ground you just drove them off of. This doesn't apply in a war that is about advancing a line.
My Taliban example works only because those Patrol Bases aren't expanding their walls or pushing a front line. In the game and in a war of maneuver, you are going to use firepower to dislodge the enemy, then take the ground they just left. Obviously they are going to return to the rubble if you don't take that rubble.