Am I the only one that really dislike this change?
First of, now region population is just a number, with no implication beyond getting manpower.
Secondly, infrastructure just affects your movement speed, not your level of industry in a region. If you already have 50 or 60 infra regions, there would be no logical reason to improve it, since it already works well enough for your movement needs.
That sounds very similar to how it was in HoI2 or HoI3.
The system before was beautiful, where you gradually improve infrastructure and industry hand in hand when you have a underdeveloped region of high density population. If you already have very developed regions, like New York or Westphalia, you would need to expand to state of the art infrastructure to build more factories there. This made the economic game have more dept, and there were more consideration to make during peacetime. Now it's just: "Try to max out your factory slots". So much lost gameplay and modding opportunities!