In my current game, I started conquering one of the Fallen empires, and I noticed some really weird construction choices.

For example, city that has no resources other then food was building smelter (bonus to metal).

One city had bunch of buildings that add food bonus, while city produced no food at all.

And another had around 8 shanties (-8 food!!!), in attempt to level up city to size 4, but there was almost no point of that, since only thing that city was good for was food production. It gains nothing from +x bonus to gold/tech/arcane. Although... it could have been attempt to get Warrior Temples. We will never know. Still, it was really inefficient thing to do.

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Anyway, Elemental economy system is very specific, since it's resources driven. And it really needs decent construction AI to make AI empires flourish. No excess buildings where not needed, stacking of +X% bonus buildings where resources are, etc...