The mistake the Germans made at Stalingrad, was bombing the city to rubble, it actually made it easier for the Russians to defend as a result.
The bigger mistake was not bypassing and cutting it off, but instead insisting on taking it.
Reading some books about Stalingrad. Even the women and children were forced to fight or get killed themselves. War machinery such as tanks were sent into the battlefield right when it was completed. They didn’t paint or even give last-minute inspections.