The biggest flaw of operation Barbarosa was winter, an over extended sully line, and a constant change of directives from Hitler.
The biggest flaw of Barbarosa was even attempting it. There was no way the Reich was going to win a two front war.
As for the T-34, I guess you could say that it was a war winning tank - but stepping back for a second, there was no way Germany would ever conquer such a large, mineral rich and populous country. If they hadn’t come up with the T-34, they would have come up with something else to overwhelm the Germans with.
And that’s what the T-34 did - over whelm with massive numerical superiority.
Another flaw was treating the locals as sub-humans when they initially welcomed the Germans as liberators. Had they armed them and proclaimed Ukraine as a liberated country there would have been much less resistance from them.