The Sherman was essentially “good enough”, and could be produced in staggering numbers. For example, Germany produced 49,000 and change armored fighting vehicles of ALL types during the war. The US produced 49,000 and change Shermans alone.
But ultimately the issue was a doctrinal one. US doctrine at the time had separate roles for light tanks, medium tanks, and tank destroyers. According to this doctrine, tanks weren’t really intended to seek out and engage other tanks as a primary mission. That was the job of the tank destroyers, and they were lightly armored, very fast and very powerfully armed relative to the Shermans. The Shermans were intended to support infantry, exploit breakthroughs, and in a pinch engage enemy tanks. So they were optimized more for that role.
Of course now with 77 years of hindsight, this looks insane and stupid. But at the time, there were a LOT of theories and doctrines that had to be proven wrong. Look at the heavy bomber offensives by all parties in the war- grievous losses up front, and then various changes and adjustments (night bombing, fighter escorts, box formations, etc…)
The British also had a doctrine that was very broadly similar, with the heavily armored and slow “infantry” tanks, and the faster, lightly armored “cruiser” tanks.
Meanwhile the Germans figured it out faster than the Allies and set up all their tanks to do most of the tank roles simultaneously. Of course, some of the later-war tanks/tank destroyers were almost purely defensive, but that’s not exactly germane here.
The US and Britain DID figure it out, but they figured it out in the Summer/Fall of 1944, and by the time they tried to rectify it with the Pershing and Centurion tanks, the war was all but over. The M4A3E8 Sherman (what Fury was), was basically an incremental improvement over the previous M4A3- better suspension and more powerful gun, but still not anything that made the Sherman anything other than barely adequate for fighting German tanks directly.
And with the exception of Gen McNair, I’m not sure that the generals were against it; I think there was just less experience. Look at it this way- the US didn’t even enter the war until 1942, and fought in N. Africa, Sicily and Italy. None of that, with the possible exception of N. Africa, gave the US good experience in mobile warfare. So we started the experience and data accumulation process basically after D-Day. Meanwhile, the Germans had been working on it since 1939- they’d seen what worked in Poland, France, and Russia, and were modifying existing designs and coming up with new ones to match.