Well, they are rectangle so that you, the player, can see the strength and ORG bars at a glance.
This is better than the HOI3 way of presenting the information.
There's some waste of GUI space there though. I wouldn't mind having more information on the counters and the grouping is just terrible and unintuitive.
With some semblance of a off-map OOB the grouping could easily and logically be done to corps/army level when zooming out which would be tremendously helpful for managing battle-plans, the icon could switch when zooming out (and the grouping happens) to numbered army symbol or something similar with averaged STR/ORG and the indicators for success/failure (that's now on the theater tab) for an even better overview on-a-glance.
It would also be very useful if the supply situation was represented when zooming out. Not as detailed as in the supply map but at least partially.
Those 5 Soviet division commanders we hand picked to hold down a special province...that increases our emotional attachment to the game and immersion, and our interest in the outcome of that battle.
Of course, clicking 50,000 times to set up your army isn't fun either. There is some balance here, and it is easily possible that I'm more sentimental than some regarding my division commanders

.
This!
Divisional flavor was possible through the generals. I would love if some randomness to divisional performance was added through automatically generated commanders. These could then be recruited for PP (just like extra generals are now) or they could pop-up as aces do for air-wings. The traits would make much more sense as well and there would be hard choices on whether to keep that good armored commander leading a division or to promote him to corps/army commander where said traits don't apply.
A lot of the new mechanics in HOI4 are great and way better than most of the features in the previous titles but some of the heart was traded for more iron. Losing a division in HOI4 is painful for other reasons than in HOI2 or 3. In HOI4 you think first of the production and equipment consequences on the strategic level while in HOI2 and 3 it was on a more immersive level and the operational consequences were the primary concern.
Likewise, losing a capital-ship in HOI4 is clearly more "meh" than it was in HOI3. In HOI3 the capital assets was something you could tinker with and every build came down to choices. Upgrades meant planning and you grew attached to the vessels in question and the detailed lists of losses meant you also learned to fear the oppositions main assets (at least in MP). Right now we don't even have consolidated statistics for our ships and going through every single destroyer or lost ship (which is in a completely different interface) in an attempt to gauge the situation at sea is just hopeless and as much as any micro-chore in HOI3.
Regarding some more form of OOB or ways to organize the troops PDS has explicitly said that it's something they have on their wishlist but there are no official details released yet.
I can understand why it was omitted in the first place since the 50k klicks from HOI3 OOB setup wasn't really a good core mechanic.