Most of this game involves careful planning and preparation to get the most out of your country and army. Building a command structure, and assigning leaders appropriately is an important element of this. Its just as important ensuring proper research techs, custom building your divisions, proper placing of divisions, and proper timing of attacks, proper coordination of units, ect. ect.
For every element of this game there will be a group of players who like it and those who don't. Those who don't like something can let the AI handle it for them. You can't say you don't want to be bothered to assign leaders manually, and then complain the automation wont make the same choices you would. If you don't care enough to do it manually, then you shouldn't care about the ai matching your preferences.
Creating Corp, Army, Army Group, and Theater HQ's are just as big of a chore, and just as important to success. Some people like it and others don't, it can be automated, but it should be gotten rid of for the same reasons as getting rid of division leaders.
Ditto for custom division creation, converting units to better types (inf to mot for example), building properly organized fleets, managing carrier aircraft, air force organization, infrastructure/ports for supply lines, dealing with frontage and stacking, building up practicals for efficient production, custom unit designs for tanks/planes/ships in the tech tree and so on and so forth. Strip them all out and revert back to HOI2.
There is no reason to strip out division leaders, and abstract away another part of the game. Features like this are what made HOI3 a huge improvement from HOI2.