How can you even confuse the icons? They are all different.

Try launching a duel between Alt Demons against Alt Demons or Alt Tier 3 Elves against Alt Tier 3 Elves. And let's see if you can immediately tell which icons belong to Tiamats and which belong to Shadow Witches. There simply isn't a background there.

Besides, the circle here is much more convenient than this multicolored eyesore and doesn't lose out in practicality.

To each their own. In my opinion, the circle is an eyesore. And it doesn't provide anything that the scale, bars, and logic provide. Because you can see where the unit will go anyway (and in the case of overlapping zones, they are displayed in red in the model).