Remember, V2 was the brainchild of Werner Von Braun. Despite being a V2, this was really a Version 1 rocket. None other existed before it. I'm sure they had plans for bigger and more capable rockets, they simply didn't have enough time/money/materials to get them produced before the war ended. Wasn't the V2 only about the last 1-1.5 years of the war?
The "V2" doesn't stand for version 2 rocket, it is "Vengeance Weapon 2". Vengeance Weapon 1 was a jet powered missile.
The V1 was fast but the allies had fighters fast enough that they could and sometimes did shoot them down in flight. Literally it's ONLY defense was speed. It didn't evade at all because it wasn't piloted so if you could get into the right place to intercept it, it could be shot down.
The other thing is that it's well documented that Hitler was not in his right mind for a long time before the war ended. They also had jet engine planes and cruise missiles that they misused. Hitler essentially ignored most of his generals and other experienced leaders.
The main counter argument to this is that it really made no difference. Once the USSR survived the initial onslaught and the US got involved, the Germans simply had no chance. If you look at production figures the British more-or-less matched German production. Soviet production was substantially higher than German/British and US Production dwarfed all of that. Nothing the Germans could have done would have been enough to dig them out of that hole.
Basically, the Germans "won" the first half of WWII by a score of 30-3, with the 3 being Dunkirk. After that they failed to conquer Russia, and then once everyone else's tactics evolved and Blitzkreig no longer worked it was all downhill.
Blitzkreig didn't stop working. Essentially it is modern mechanized warfare as it is still practiced today. The problem for the Germans wasn't that it stopped working it was two things:
- Everybody else caught up, and
- Scale.
The scale issue is the most fascinating thing about WWII to me. When Germany invaded France in 1940 they had ~2,500 tanks. Three years later they had ~3,000 tanks at the Battle of Kursk and that was just one battle on the Eastern Front and they were easily outnumbered by superior Soviet Tanks. Two years after that the Soviets hit Berlin with more than 6,000 tanks. Ie, the Soviets had more tanks facing just the City of Berlin in 1945 than the Germans had facing the entire nation of France five years earlier.
The Germans simply couldn't keep up with the expansion in scale.
One thing about the German army of WWII that most people don't realize is that it wasn't all that mechanized. They had highly mechanized units at the tip of the spear but the vast majority of the German troops that went into the Soviet Union walked and most of their gear was carried by wagons pulled by animals. In the US, UK, and USSR armies of 1945 not only was the tip of the spear mechanized, the entire army was mechanized with Studebaker Trucks (including for the Soviets) handling the logistics.