The EB games spend a colossal amount of attention on things like unit looks and differentiation between the factions down to the level of common shield devices. I can't fault them for that. However, they're still tied to the Total War combat engine, and all of the historically inaccurate crap that implies.
You look through ancient sources (assuming you actually believe them), and you see most Diodochi era battles have a loser's casualty percentage somewhere in the 15-20% range, with the winner's casualty rate being considerably lower. Rome's fights tended to be a bit bloodier, but while you have some famous battles like Cannae and Trasameine and Telamon with huge losses, those battles became famous precisely because they were so uncommonly bloody and decisive. You actually play the game, and the 'once a unit routs it doesn't do anything but run away and is impossible to rally with a nearby enemy so one cav unit can mop up half an army' and add in the extra armor to attack ratio that they do, and suddenly you don't get units breaking at all until well past those casualty points, and when they do, complete annihilation of the routing army is the norm, not the exception.
In some ways, EB makes it worse, because raising new armies, especially in EB2, is crazy expensive, so the sudden loss of a big force (almost inevitable when battle is joined) usually leads directly to the annihilation of the power fielding it. Again, this is just not how ancient war worked, even for the diodochi, who were relatively unstable in regards to ability to absorb major battlefield defeats.