Really? I thought it was the single best thing they have ever done. It took combat from being just a mindless, meat-grinder where you stack as many units as you can in a single square to something where you need to think about the terrain, army composition and your attack strategy.
You clearly havent played much of the older Civ-games if you thought it was all about stacking as many units to win before. There are alot of problems with the 1upt-system, but I can add some of them:
1. Civilization is an empire-building game, not a tactical game. I think this is important on a general level, the series was always about building your empire, getting much production and so on, and I think its the skill in this part of the game that should be the most important - as it was in all 4 prior civ-games. This also means of course, that bigger is better and will beat smaller armies, most of the time. Just as in any other strategy-game like Starcraft etc. The 1upt-system had to drastically cripple the amount of units you could build to work, and as a consequence made the whole empire-part of the game dumbed down, easy and ultimately less interesting than in previous games.
2. The maps are not built for 1upt, and that always creates "bottlenecks" that forces you to heavily micromanage unit movement - something which was way less busywork in earlier games.
3. The AI can not keep up. At all. Im sure it feels good to outsmart the stupid AI, but from a gameplay-perspective, this is the single biggest flaw of civ5.
4. All the subsystems had to be designed to accomodate for 1upt. When combat featured fewer units, production was slowed down, meaning the game became more boring, so Firaxis had to develop other stuff to do. What they came up with was a lot of "random bonus if you do x", which took even more away from the strategical nature of the series. In Civ4 in particular there were a lot of interesting decisions to be made that also played a huge role in what empire you forged. In civ5, what kind of city state you bordered was often more important than the choices you made yourself.
My last point goes back to what i said first. Civ4 in particular was not AT ALL about only stacking, even though production superiority was more important than tactical superiority (since even the AI understood how to play the game at a basic level). First, there was the rock/paper/scissor-design of the units, meaning you always had to balance your armies. Second, there were siege weapons that could be sacrificed to reduce the hp of all units on a tile, thirdly, there were the possibility of going around your enemies to take out vital resources, citites or just kill workers (which the AI used to great effect). This fourthly, meant that you most of the time had to spread out your army to defend your border, which in itself is completely different than the cliche of "stacks of doom". I could go on about this. But the point is that
combat is way deeper in civ4 than in civ5.
And I therefore hope they go back to the deeper, and more strategic experience of Civ4 and of course develop that further.
Edit: But why take it from me, even the game's
lead designer Jon Shafer thought the 1upt in the end did more harm than good.