A sixteen pgs. paper from MWI @ West Point and near the start a passage:
At the most basic level, however, there is an obvious, but neglected tactical problem in city fighting:simply crossing the street.
The amount of damage and numbers of casualties in fighting in recent years in Raqqa, Aleppo, Marawi, and Mosul show how rudimentary urban warfare tactics remain, as well as the highly destructive nature of combat in cities. Without new tactics and tools for dealing with some of the basic challenges of urban combat, military units are forced to employ extremely destructive methods to reclaim cities from entrenched defenders.
Link:https://mwi.usma.edu/wp-content/uplo...the-street.pdf

I noted a reference to Hue Citadel in 1968, with 90mm tank cannon being found to be useless; my understanding is that the USMC realised only the "big guns" could breach the walls, so called up 155mm & 8" guns to batter a hole in the walls. When the ARVN mounted an assault the NVA/VC had left. Less certain is the tale that the USMC in Hue after a few days called the USMC Library @ Quantico, where a librarian explained how siege warfare had worked and so they reverted to those methods.

Plus the reference to defenders who were willing to die, citing ISIS in Mosul as an example. Yesterday I watched a YouTube documentary on the Canadians assaulting the walled city of Ortona, Italy in 1943 held by German paratroopers, as relevant today as it was then.
Link:https://www.youtube.com/watch?v=-SO7MoWh48g