As Jon Shafer, lead design of Civ V put it, Go is a game you can learn in about 30 seconds. Each player takes a turn placing a single stone on a free spot on the board, once surrounded by the other color (black and white) a group of stones is considered "captured" and is removed from the board. Last color on the board wins.
Not only does this have vastly less rules than chess, it is a game orders of magnitude more complex than chess. It took an extra 20 years of computing advancement to go from beating a human chess champion to beating a human Go champion.
"Stacking" is not only totally unnecessary to have a complex game, and makes the game harder to actually learn or play at all, but it also gives you less decisions to make. If you can't stack you have to decide what order your units are in, you have to pay more attention to how they move across the board, etc. That Civ hasn't done a great job of making combat the most fun, stacking or not, does not bear much on the inherent advantages or disadvantages of stacking or non stacking.
The other half of the original Go quote, which I heard from a Japanese Go player in college, was that it takes 30 seconds to learn and 30 years to learn how to play well.
One good point here, though, is that much of the dissatisfaction with either 1UPT or Stacking with or without limits is that no Civ game seems to have handled the consequences of those mechanics well or given us a combat system appropriate to the time and distance scale of the game or the place in the Chain of Combat from which the player is making decisions. After all, if in the rest of the game we are playing as the Near Omnipotent Wonderous Spirit of the Civ, why are we deciding which archers and in which sequence will fire at which enemy Warrior?
On the other hand, there is a sub-set of players who want to decide which archer is firing right-handed and which left-handed and wants to get the most out of each of them. So IF the game wants to accommodate everyone who ever turned on a computer, Decision levels have to be adjustable from Grand Strategic (the rest of the game) to Tactical (the Archer Company of Aethelwurst-on-the-Dung).
I think doing that will mean having:
1. An AI that can do almost as well as the gamer in almost every case, so all players with the slightest streak of competitiveness aren't forced to handle every tactical decision themselves.
2. An appropriate level of Non-Control over the tactical situation - appropriate to the technology, social and civic policy levels of the armies. This, not incidentally, will help make the AIs job easier (and more programmable, hopefully) because for a long time and in many armies that reduces your tactical decisions considerably. A Greek Hoplite Army, for instance, has 0 tactical decisions: the
strategos fought in the front rank with the rest of the phalanx and couldn't influence anybody more than 10 paces away once the battle started: any 'tactical decision' he made had to be made before the battle. You want to make detailed tactical changes in the middle of the battle, that limits your options throughout most of history to things you did before reaching the battlefield or at least, before the first spearpoint hit the first shield.
3. Some way to decide the Entire Battle within a single turn. This is a no-brainer. When the smallest game-turn is 1 year, only the occasional siege lasts any appreciable fraction of a turn. At the other extreme, the entire Battle of Kursk in 1943, considered one of the largest land battles in history involving almost 3 million men, over 3500 tanks, 3000 aircraft, 25,000 artillery pieces, and involving a multitude of individual attacks, retreats, advances, and tactical maneuvers, was decided in less than 2 weeks - or less than 1/100th of a Game Turn.
Solving those problems, I think, is far more important than whether the game allows you to stack 1, 3, or 50 units in a tile - although I freely admit, I think some kind of 'massing' of individual units, however it is done, is unavoidable to maintain the battle within the time and distance scales of the rest of the game.