I'm sorry to hear the AI is still rather sorry. That's the #1 reason I haven't bought the game, and was one of the top reasons I didn't play 5 as much as III or IV. I like there to be at least a chance that I'll be caught off guard by a sneaky AI. And there are games where that happens nowadays. Paradox's AI isn't perfect, but I do have to follow Sun Tzu's maxim about victorious warriors winning first, and then going to war, and I've definitely wound up a target of an opportunisitc AI realizing I was a bit overextended from other conflicts. In Civ5, I could go to war first, and then seek to win, and reliably win, and it sounds like the same would apply in Civ6.
Whereas in III and IV, the AI could occasionally legitimately take cities, and if I was poorly prepared, win a war. I'm experienced enough in III now that losing at a fair game isn't going to happen except with the worst of start positions, but back in the day there were some back-and-forth wars. IV takes it up another notch in AI, and while I'm still unlikely to lose in a fair game, it doesn't take much of an AI advantage for there to be a real chance that I won't win.
Granted, Karpius is right that there are a lot of more casual players. I have some friends who play Paradox games with cheats so that they can essentially defeat whoever they please. To me that isn't fun - I want at least somewhat of a challenge - but it suits them, and likely many others.
Nonetheless, I am disappointed that Firaxis still only has one AI programmer. They had one AI programmer for Civ III (Soren Johnson, prior to his design work on Civ4), and now it's more than 15 years later, they're a considerably larger company, their Civ revenue must be way higher, I'm sure they have more artists, and they still only have one AI programmer for Civ. I don't expect an army of them, but I did hope they would have scaled it roughly proportionally with the success of the series, to at least a small team by now. Maybe with so many complaints about the AI, and the consequent impact on the reviews (especially user reviews), they'll finally do that for Civ VII.