Man I hate 1UPT. Not the principle itself, but the way it was executed in Civ 5.
Look at how 4X games have dealt with combat in the past.
On the one hand, you've got games like Civ I-IV, Europa Universalis, Dominions, GalCiv, etc, where combat is abstracted. You send your guys into battle and some sort of representation of combat takes place,
On the other hand, you've got games like Master of Orion, Master of Magic, Age of Wonders, Total War, Heroes of Might and Magic, where combat is fully represented. You send your guys into battle and it takes you to the battle screen where suddenly your stacks have been split up into a 1UPT battlefield.
Civ V tried to be both at the same time. And honestly? It didn't really work.
Games that abstract combat generally do so because combat is only a portion of what the game is about. You need to construct buildings, develop new technology, manage your population, conduct espionage, balance your budget, and negotiate with other nations. I don't want to spend half an hour on the battlefield, I want to take care of this situation and get back to running my empire. Civ V's system is too clunky and micro-heavy for this. Repelling even a couple of barbs is far more tedious than it should be.
Games that don't abstract combat generally do so because combat is a significant part of those games. While Master of Orion, Total War, and even AoW and HoMM all have empire-building elements, the emphasis of the game is quite markedly on the combat. Master of Orion 2 and Master of Magic are kind of grey areas here, as they kind of have an equal emphasis on both, but hey. And the thing is, even though some of those games have fairly simplistic combat (at least compared to wargames, or even something like Panzer General), it's still far more robust and has a lot more depth, excitement, and functionality than Civ 5's combat, which is fairly lackluster.
tl;dr: Combat in 4X games can either be abstract or fully realized. Civ 5 tried to do a compromise and ended up with the worst of both worlds.