Once nuclear arsenals and strategic deterrents reach levels that allow MAD to fully kick in it all changes, as HoI4 is absolutely unequipped to represent that reality.
My take on this is that HoI4 can (somewhat) adequately cover the geopolitical situation and warfare of the world up until the 1960s. I've given this question a lot of thought as I made a mod entirely dedicated to it (Extended Tech Tree 1960).
