It’s not that I disagree with what you are saying. It is obvious to me that Firaxis’s places very little priority on AI.
But I also think that how much someone minds that depends upon their perspective. The more you are picturing playing a competitive game – particularly a conquer-the-map military game – against quasi human opponents, the more this will drive you nuts. And that is pretty much what a large number of people here are looking for.
But I look at this as a building game, where the emphasis is on providing interesting and varied hurdles to successfully building a secure nation. The neighboring civ is not a symmetrical competitor playing by the same rules and with the same goals so much as a hurdle who will likely require time and resources to handle one way or the other.
A parallel could be made to the typical RPG. The enemies you fight rarely have any real chance to beat you, they are not playing the same game you are. They are just hurdles to overcome.
The thing is that Civ VI (in my opinion, much more than Civ V) makes the hurdles much more interesting and diverse. Maps vary, start locations vary, opponents vary, etc. Which, in my book is great, but it makes it all the more impossible to write AI that could pass for a symmetrical competitor. My assessment of it is that Firaxis was just realistic about what this game really is and what it is not. In my view, they made the right call, in that it would take a total re-write to make this a game that could really compete for the wargame market.
However, unless you do some rather gamey or exploitative things, you can have dozens (probably hundreds) of hours of gameplay where the obstacles provide interesting challenges, and this can be dramatically extended if you play some less-than-ideal civs, play through poor starting locations, don’t save-scum, etc.