That's what Jon Shafer did for Civ V. The result was horrible.
The AI should not be programmed to just try to win. That is not what most players want, and that would make some victory conditions impossible and the game less rich (currently it's religion, before that it was diplomatic victory).
The AI should not be designed to game throw. You are saying it should be.
If attempting to win makes some victory conditions less viable or not viable at all, that's a condemnation of the design and balance of the game. The AI is acting as a player in the game, and as such it should be playing the same game. If chunks of the game become non-viable when AI diplomacy is replaced with humans, there are chunks of the game lacking in design viability. If you make a system someone would actually use in MP, you can then tune AI to use it without it being functionally worthless. That's what we should have seen, but don't.
I've seen attempts to make a case that the AI instead taking on the role of a spoiled child flipping a table is good for immersion, but that case has never been particularly sound.
Every civ game has had flaws. The AI's propensity to game throw *by design* was a major one in Civ 4. What Soren said sounds nice, but what happens in practice isn't. 4 is still more challenging than newer entries in the series, simply because of the scale of bonuses and that AI can handle stacking its super discount units in one place better. There is no civ 6 equivalent to 15+ unit rushes at 1000 BC. "Just build 3 archers" is a viable deity survival strat now.
Civ 6 has lots of things in release that surpass its predecessor. The tall vs wide cancer is less prevalent/reasonable, there is a least reasonable depth in builds, and interactivity with situation is something lacking in 5 that is at its highest point now. Those are positive changes.
Unfortunately, civ 6 has not found a way to tackle poor UI, and has only somewhat helped performance. The unit cycling is particularly terrible, and forcing an ini edit to remove that doesn't address the unit control issue entirely. Ranged units got buffed by the terrain change, the exact opposite of what needed to happen with ranged units. Civ 6 is a mixed bag, it also isn't finished. That's not an acceptable thing.
Edit: Random events can work, but Civ 4's were a joke and if that's the best we can see in Civ I'd rather never see them again. Hedging against risk with incomplete information is reasonable. Losing 10000 hammers instantly is not, nor is having a random-something that does nothing at all to influence your strategy in any capacity whatsoever.