I've played many hours of HOI4, mostly as Germany. I have tried to get production and construction up to historical numbers, but have never succeeded. It doesn't seem possible to me to produce and construct all the things that Germany did historically during the war. In fact, I never even get close.
I suspect this is a problem with every country in the game due to the current mechanics. One problem I think is the large debuffs that some of the laws cause. I kind of doubt that those laws are accurate and realistic. Another factor that I think is completely missing is the large amounts of forced labor that the Axis countries used during the war. Millions upon millions of free laborers doing all manner of work. This allowed the Axis countries to punch above their natural weight I think. And this large labor pool is not really being modeled at all currently.
I suspect this is a problem with every country in the game due to the current mechanics. One problem I think is the large debuffs that some of the laws cause. I kind of doubt that those laws are accurate and realistic. Another factor that I think is completely missing is the large amounts of forced labor that the Axis countries used during the war. Millions upon millions of free laborers doing all manner of work. This allowed the Axis countries to punch above their natural weight I think. And this large labor pool is not really being modeled at all currently.