IMHO, the Soviets alone could have eventually defeated Germany, thought at much greater cost (as if over 20m casualties wasn't already incredible).
But the Nazis self-sabotaged constantly. The Panzer IV and the Stug III (with the outdated Panzer III chassis) were arguably the closest standard for armor, but they were constantly diverting effort to alternative platforms that were too complex to mass produce and maintain. And the same for other weapons.
The problem is that the early WWII arms race was so fast that I don't know how anybody can say with confidence that Germany lost to worse tanks than theirs. By the time the allies got any volume into battle, they also got better designs than their earlier ones.
And people don't really know much about the tanks the Germans were using in France and in Barbarossa. The Pz 2 was used extensively in Barbarossa and it was intended as a training tank! The Pz 3 was woefully underarmed compared to T-34 and god forbid come up against a KV1.
But at the end of the war, the Panther was one of the best tanks on the battlefield. Good crew ergonomics, a gun that was perfect, optics that allowed it to be used well. Comparing that to even a Firefly Sherman? Not a fair fight.