Stack of doom don't work in the real world, though. They only did until napoleonic times or so.
Trying to do that with modern armies just leads to something like the French army of 1940, cut off from its supply bases and command.
However, 1UPT is not the good right solution. Supply and encirclement, like in Shadow Empire is.
The problem is the scale, army structure and how the battle is fought.
Also what do people want to play in those games.
In the past the distinction between battles and grand tactics is not as important as it is in the modern time.
Civ is a game that try to cover entire human history with one chess-like battle system.
I don't think majority who play civ really care about how real war is fought in civ. If one care too much, Civ's battle system will only make them headache.
One can't tell the scale of the unit, everything is abstract in Civ.
Is that infantry man represent one division or one corps? why do the player need to give order to a machine gun unit when we are playing as the supreme leader of our nation?
The doom stack is good in that it simply represent the total military strength of your faction in a pure abstract and streamlined way. A very mass market tabletop game design, which is what Civ is.
One can't even tell what exactly one hex mean in Civ.
is it a solid space of land? for example 5km^2? or is it just an abstract idea of space?
1UPT system is for people who want to play civ but also want to have a chess like tactical aspect to it.
It is the sin of most 4X game, they are not proper wargame. Because audience tend to be difference.
doomstack is less of a sin because at least the game is completely focus on strategy and 4X aspect.
Where 1UPT is making the mistake of adding unnecessary tactical details into an abstract strategy game in the wrong scale.
Not to mention the whole AI thing.
Morever, a larger scale strategy/operation game tend to be more like GO instead of chess. Where unit is more uniform without much chess-like hard counter that force you go for a 1 or 0 binary situation.
But most 4x ofc can't do that in the late game, people want tacticool and unit diversity.
Most people want to play tactics such as placing pikeman in a place to counter cavalry and archer kiting tactics on a strategic scale map. Thus 1UPT is almost a guarantee for popular title like Civ.