The AI may be "trying", it just might not be trying to do what you envision it should do. There has always been a spectrum of players who play this game differently and thus envision its perfection in different ways.
"Trying" implies attempting to attain one of the victory conditions as defined by the game. In addition to its usual tactical failures, the AI is *intentionally* designed not try at the strategic level. This is not a respectable choice and players should not respect it.
People can open up Civ 6 then not play Civ 6 (up to and including literally, such as going to do laundry while the game is open). If they're not in MP that's their sole prerogative. If they are in MP and their opponents didn't agree to them doing that they should be kicked. This choice has no bearing on the AI regardless.
Many expect the game to be more of a simulation of human activities, responses and perceptions. Flawed, in other words.
What's flawed is the reasoning used to make such a case. An arbitrary amount of "simulation is okay", but not other times. Simulation is okay, until it isn't okay.
Incoherent logic should not inform game design, or most decisions for that matter. And incoherent logic is what is being used to "expect the game to be more of a simulation of human activities".
What do actual human activities in Civ 6 look like? I bet they're different from the AI's activities, even among the players purporting they want to role play. People will "role play" then complain if they lose to the AI attacking them. That's not credible rationale and it shouldn't be treated with any meaningful weight in the game's design. Players making that case are necessarily irrational in that context.
These folks would expect the AI to go about its business and make decisions in the moment without knowledge of how to end the game in the future.
Those are expectations of active dishonesty and self-inconsistency. The game has clear incentives. Historical leaders acted on historical incentives. In a scenario where "historical" AI are ignoring their incentives,
the assertion that it is a "historical simulation" is objectively false.
I don't profess to know how good or bad the AI is, but in this game, the devs have to straddle the different play style expectations and that isn't easy.
They get no such pass for this. Design the game first, then make the AI play the game. If they think the game would suck if the AI actually plays it, maybe they should rethink their design.
The issue isn't if AI can beat a human in Civ. The problem is it would suck to play against. You would see things like ICS and tons of units and a bunch of chopping/pillaging.
Can you make an AI that is competent at playing to certain victory conditions without min/max style play.
If the AI playing the game optimally isn't fun, the AI isn't what's at fault with the game. The game's design/rules/victory conditions are what's broken in that case, not the AI.