So I've been intending to do a longer post here for awhile, mostly to flesh out the criticism I posted before on the combat and unit design as lazy and to address some of the apparently common defenses of 1UPT/MUPT. Instead of a mass of confusing quote-responses, I'll sort the thoughts by heading here:
Strategy, Operations, Tactics
At heart, Civ has always been a strategy game. You set a long-term objective, and leverage your starting position, resources, units, etc. to reach it. There are specific tactics that can be used in service of that goal, but it's not a tactical game, whether a tactical wargame or a tactical trading game, etc.
When you fight a war in Civ, you are basically working the operational level--you allocate resources and troops to a front, you oversee the marching campaigns, you promote your units with a particular doctrine in mind, but you don't fight the battles; you just see the odds and the results afterwards. The "tactics" people talk about, whether 1UPT maneuvering or MUPT stack positioning, aren't. There's not a more polite way to put it.
Lazy Design/Problems with Prior MUPT
Thus, this brings me to the core problem Civ has. It is a strategic/operational game series that religiously refuses to implement or improve upon game mechanics in this direction. The only serious rule I can think of is Civ2's zone of control, which was an interesting step that was initially removed then added back into Civ3 in a very confusing fashion. Bombardment has been handled in a schizophrenic way over the course of the series, from suicide cats to WW1-style tile barrages to superhuman archers launching arrow barrages 100 miles away.
The ideas they have never explored would have naturally limited stack sizes like supply chains. Farmland and railroads can support more troops passing through than the Alps, that should be reflected in an operational game. The units have always been of ambiguous size and any sort of army organization has been missing in all but Civ3 where you had armies formed out of multiple units. There is no reason why Civ shouldn't try to model at, say, the brigade level for a manageable number of units, and then allow players to build command structures that simplify their warmongering. There's no reason why we shouldn't have simultaneous turn execution--you give your generals orders to carry out, then everyone starts moving at once and you see if your attack was well-placed. The stacking doesn't necessarily take into account frontage, which is a Thing. Oh yeah, why don't stacks fight as one instead of the silly gladiator model we have been stuck with for years? There is not even a separate consideration for the number of troops (unit strength) and how ready those troops are to fight (i.e. cohesion, organization, morale, Bueller, Bueller?)...
I can go on, nearly forever.
1UPT
So much to write here... the first is about scaling. Awhile back, I did the calculations for what a tile on a Civ4 map represented when scaled to the globe (it was on the order of hundreds to ten-thousands of square miles depending on map scale), which is a huge chunk of land that could fit millions. The spatial crowding argument is frankly a load of bull that over-corrects the frontage problem. So is the idea of limiting stacks to sending out one gladiator per turn. Which is why it pains me so much to see it, because there is a real thing that could be addressed here but instead it's done in a ham-handed way.
The ramble-comment zone: Aeson addressed some of the abstraction issues here already, I'm in agreement there. The argument against limited units per tile (LUPT?) in favor of 1UPT basically ignores the solution to Civ's real problems for imagined shuffling problems, Santoo appropriately notes that you don't have infinite units and resources to shuffle optimally before combat every time. Lucius's note on soft units needing to be squishy can be accomplished in different combat models than the gladiator system and positioning is important outside of 1UPT system. At least some vets like TMIT made that point. Same on the luck v. skill thing.
Abstraction
This leads me to my final point: I understand the Civ systems are abstracted, and I advocate for abstracting real-world phenomena in games like these because you can only fit so much in before it becomes confusing and unplayable. It's not realism for realism's sake, it's not abstraction for abstraction's sake, it's abstractions that are intuitive and fun. 1UPT and the prior-implemented MUPT don't meet this standard.
Also:
One note though. 1 unit IS an army, likely representing an entire platoon. Some people here apparently think a swordsman is only representing 10 guys or something.
Well played, buddy.