The problem was in Cassino was that they bottle-necked due to the wreckage caused by the Allied artillery and aerial bombardment. They really were crawling up those streets and through those valleys. All of those during the Cassino fighting were extremely brave.
On the point of armour, the whole idea of the Sherman was not to crawl but to "run" so to speak. Fast moving targets were extremely hard to hit. However, the Germans were excellent at concealment. It's awful image to watch a tank's turret disconnect when you know there's people inside that thing.
The German forces out-gunned us throughout 1943 and all the way to 1945. The only thing that the Allies had was the Sherman Firefly that could punch at German ranges, and even then it struggled. E
Even when the Allied tankers saw their opponent, it would be a race to get to them before they could hit you. An extremely scary time! The Soviet tankers fared no better in their T-34s. In fact, it was known for a Tiger to merely point it's cannon at a Soviet tank and the crew would abandon.