AI verisimilitude
Verisimilitude is defined as the appearance of being true or real. Something doesn't have to actually *be* real, but at least it should do a good job of appearing that way. Arguably verisimilitude is what AI has been making the biggest progress in last year. People are using ChatGPT to get advice on things, which is kind of crazy, especially for things like stock tips. ChatGPT doesn't have a clue about stocks, nor does anyone really know which stocks are going up or down, but ChatGPT does a good job of giving advice that sounds as if it was given by a human who knows about the subject.
I am currently playing Millennia, and I am having a lot of fun with it. But I agree with one of the frequently cited points of criticism, which is the lack of verisimilitude of the AI opponents. Or as other people express it, the AI opponents have "no character", "no personality". That is a combination of two things: First of all the diplomatic game mechanics in Millennia aren't great to start with; but second the AI seems to decide on its diplomatic stance on a turn-by-turn basis, with absolutely no consistency: The AI might reject your demand for peace one turn, and then offer you peace the next turn. You are also very likely to get a bunch of messages at the end of each turn in the latter game where AI opponents change their diplomatic status with each other very frequently, which looks kind of random.
While the lack of verisimilitude in Millennia is true in isolation, it is made worse by Millennia being roughly in the same genre as, and possibly competing with, Civilization 6. And while certainly not perfect, the diplomacy system in Civ 6 is a lot better, and more importantly for this post appears as more real to the player. In Civ 6 you have nicely animated, somewhat cartoonish civilization leaders, which already improves things by putting a face onto the AI you negotiate with. And the Civ 6 leaders have both a public and a hidden agenda (which you can discover), for example Cleopatra likes civilizations with a high food output. That gives her character a certain consistency during a game, and the player an option to influence diplomacy with her in a foreseeable fashion.
Millennia is sharing a problem here with Humankind: Civilization 6 actually has civilizations that remain through the whole game, Millennia and Humankind have factions which change in each era. One could argue that Millennia would be better if instead of calling the AI opponents by the name of civilization, e.g. Germany, they would just be called "Yellow Faction". It would actually be an improvement if at least Germany with the yellow flag would automatically be assigned the color yellow for its borders; right now border colors aren't linked to flag colors, which can make the game a bit confusing, unless you do like me and during setup take care that the colors match. But the fundamental thing is that if you play against the Germans under Frederick Barbarossa in Civ 6, there will be certain consistencies in patterns of behavior with other games against the same leader; while in Millennia playing against the Germans doesn't tell you anything from one game to the next, as they might be peaceful naturalists in one game, and aggressive raiders in the next.
Theoretically future patches and DLCs could fix Millennia, and create a larger set of AI opponents, which then could actually have preferences for certain national spirits and thus playstyles. Leader pictures, at least in 2D, could be added. Diplomatic stances could be made more "sticky", so as to provide more consistency. But honestly, I doubt that will happen. This doesn't seem to be a core concern of the developers. But it sure is a concern of players, and Millennia's success is suffering because of it (obviously not *only* because of this).