Why anyone should imagine their judgments regarding the quality of one of our generals or another should be respected is a good question.
A German Error of major consequence ~ how to build tanks. The Germans built large tanks and effective tanks ~ but yet they built them slowly since they'd decided to hand the work over to folks who usually built locomotives.
The Allies made use of automotive manufacturing capability ~ people who built trucks ~ and they could produce tanks, or chassis for use in Russia, quite rapidly.
In the end the best of the big German tanks proved totally inadequate. The Allied tanks were a stupendous success.
My dad and General Christmas regularly flew to various cities throughout the American heartland as the General saw to the production and deployment of tanks and other American rolling stock for the war ~ you almost never hear of General Christmas ~ BTW, there were two of them ~ the guy meeting with company engineers and executives in Detroit, Indianapolis, Chicago, St. Louis, Louisville, etc. was actually far more relevant to what went on in Europe ~ and Russia ~ than Patton or any other field general.
That's why he got to hop around in the most luxuriously appointed and capable aircraft owned by the US government ~
FWIW, after the war General Lee was asked which of the generals he faced was the toughest opponent.
His answer? McClellan.
Really?
The Germans called the Sherman tank "the Ronson", because one hit and it would blow up and catch fire.
The mechanics of the Sherman were very good. But the tank was underarmored and undergunned especially against heavier German equipment.
Arguably the best tank of WW-2 was the Russian T-34, which was diesel, heavier gunned, very fast and was the first to make use of sloped armor, which greatly improved protection.