The AI in Civ 5 was its biggest failing. It's not like the AIin Civ 4 was so much better, but it handled the game mechanics better. The change to 1 Unit Per Ti

The AI in Civ 5 was its biggest failing. It's not like the AIin Civ 4 was so much better, but it handled the game mechanics better. The change to 1 Unit Per Tile in Civ 5 and 6 basically brought to the forefront the weakness of the AI in Civ, because in 5 and 6 the enemy AI can't place military units worth a damn. They can't take cities properly because they spend turns just moving siege units around aimlessly. They are easy to kite because they have no concept of effective unit placement. You can win military victories in 5 and 6 against much stronger opponents and on harder difficulties because the AI just cannot cope with the 1UPT mechanics in any meaningful way. I've had entire games as well where the AI just never built naval or aerial units at all. All I needed to do in that situation was be England and build some ships and I'd basically won. This was on the difficulty one notch below Deity as well. Civ 4 is still the pinnacle of the series, not because it has better AI, but because that AI can simply deal better with the mechanics in the game. Stacks of units, while having their own problems, at least allowed the enemy Civs to pose a challenge.