1upt is stupid. The game is strategic, not tactical. A battle between four spearmen, three cavalry and four archers should not take up half a continent.
The only thing stupid about 1UPT in Civ 5 is how it was implemented. Do not confuse the idea with the implementation. It's perfectly possible to make a 1UPT system without the problems you've described.
What most people seem to forget is that SoD is a 1 unit per tile system. If you are forced to use all units in the same tile (cos the AI does the same) then you have essentialy a 1 HUGE UNIT per tile system. But you control what parts of this unit will fight at a time and the parts involved in both sides fight individually, so it's the same nonsense problem that you've pointed out: the same way "a battle between four spearmen, three cavalry and four archers should not take up half a continent", also a battle between 2 massive armies isn't resolved by small parts of these armies individually dueling each other while the rest sit and watch waiting for their own turn.
That's the problem about these discussions, people are confusing the idea with the implementation of the idea and that's exactly why these discussions leads to nowhere.
There's perfectly reasonable solutions for both SoD and 1UPT that could be implemented in Civilization series, but no one wants to talk about that, they just want to defend something that has been (poorly) done as if there's no other way of redoing it. People are lazy of thinking by themselves.
Both the 1UPT system of Civ 5 and the SoD system of Civ 4 are ridiculous outdated bad-implemented unit management and combat systems.
The waste of time discussing which is worse or best, instead of declaring both as badly implemented and sugesting a better way to implement them, is the very reason why Civilization 6 will continue to have a ridiculous system, no matter what they chose.
Mark my words.