That being said, there's hypothetically a UI that can make this all magically less of a burden, but even when I play other GSGs, I see how hard it is to present information to players in an intelligible way.
In conjunction with tutorials that walk through the UI.
The good example for me is Steel Division 2. It's campaign maps (dubbed the General Mode) are really good but is not necessarily intuitive. The tutorial walks through the most basic -- the basic rules, and the UI -- nothing else. With that, the player can then focus his learning and intuition on the actual game dynamic -- in SD2, that's all the in real time strategy mode. In HOI4, in contrast, I'd say much of the UI requires reading upon elsewhere.