Two things. One, to much early exploring. By the time the explorer unit can be acquired all available land is filled up. For Civ4, my suggestion is EU still attrition. Should be easily applied to a turn-based game.
Second, to much early city building. Not sure of best fix right now, but I know at the beginning of civilization, man had many obstacles to over come besides other men. I wish more randomn events besides disease in flood plain was insituted, and that these events would apply to AI also. Early games now are a big city-building race, or warfare on a massive scale. Have not come up with cogent fix yet, still cogitating. Not even sure if I am the only one who thinks a fix is desirable.
Second, to much early city building. Not sure of best fix right now, but I know at the beginning of civilization, man had many obstacles to over come besides other men. I wish more randomn events besides disease in flood plain was insituted, and that these events would apply to AI also. Early games now are a big city-building race, or warfare on a massive scale. Have not come up with cogent fix yet, still cogitating. Not even sure if I am the only one who thinks a fix is desirable.
In Civ 3, the human can either rush to fill in every spot (REX), or focus on a core empire. In the long run, most people will agree that a larger empire is better, and therefore the AI aims to achieve that through what you call 'settler diarrhea'. Do I like it? No. I don't want either the AI or the human to be able to do it, but the AI will do it no matter how you mod values because it's designed to do it to prevent the human from getting an advantage. That means the human has to do it also to keep par with the AI.

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