IMO the biggest deal here was the Royal Navy. The UK started the war still clinging on to an empire that included almost half the world. They protected that empire with the biggest navy in the world. That meant that once Germany went to war with Britain by invading Poland, Germany couldn't ship in anything via the Atlantic or via the Mediterranean. When they were allies with the Russians, that at least meant that they had access to everything Russia had in abundance, but when they did the ol' red beard thing, they were boxed in on 4 sides. Meanwhile, their enemies late in the war had become manufacturing powerhouses with access to vast amounts of natural resources.

The whole story of U-Boats in WWII is really a story of how outmatched the German navy was. Rather than going toe-to-toe with the Royal Navy, the Germans had to snipe some of the constant shipments of goods flowing into the UK from around the globe. Even at the peak of their military power, they had ceded control of the seas to the British. Their only real naval force were stealth craft that could ambush and then run away. Since the British and then the Allies controlled the seas, it allowed them to invade by sea, first Sicily and then D-Day in France.

So, without the Royal Navy, Germany would have had access to goods from around the world, and wouldn't have been vulnerable to an invasion by sea in the later stages of the war.

As for Russia, the bigger deal about getting within a few km of Moscow was that at the same time they were also getting very close to Baku. If they'd managed to control the Azerbaijani oil fields, it would have cut off oil supply to the USSR while gaining a huge oil supply for themselves.

What the Germans did in WWII was very impressive, especially considering that 15 years before the start of WWII the German economy was in such a state of collapse that inflation was running at 3 million percent per month. Prices for regular goods doubled every 2 days. Kids were playing with stacks of bills because those stacks were effectively worthless. Germany went from being the losers of WWI paying massive reparations that destroyed their economy, to being a force able to conquer virtually an entire continent. Unfortunately, that continent lacked critical natural resources and so eventually they lost because they couldn't keep up with the manufacturing powers of their enemies.