It's fun to discuss alternate history. If Operation Barbarossa had begun on schedule, instead of being delayed six weeks by the Balkans uprising, it is possible that the German Army might have taken Moscow and greatly weakened if not entirely defeated Russia. Then they might have turned west toward Britain with a more secure Eastern Front. Russia was completely disorganized during the early part of Barbarossa - Stalin was killing generals who had "failed", etc.
"Those who fail to learn from history are doomed to repeat it!"
The common belief is that Barbarossa started late because of Operations Punishment, Marita, and Mercury. They played a role, but the winter of 1940,the very late Spring thaw, and the unfinished equipping of new German formations [especially with trucks] would have delayed the attack until at least June 15th in any case. And remember, the Germans sat in Smolensk for almost a month arguing about what to do before they executed the Kiev encirclement.