Not a bad game, but sadly abandoned after less than a year after release:
They sold an Expansion Pass and pumped out the content as fast as possible to then abandon the game. This has a certain ick to it.

Released March 2024, last updated December 2024. I wouldn't have an issue with that except there are still so many issues with the game. For my personal example, the age of utopia, that let you build underwater cities, is horribly half-implemented. Since you can't station units in the cities, if you integrate it, the unrest is completely unreasonable. Maybe I'm too used to other developers continuing support and development for longer then 9 months, but its left a bad taste in my mouth that ensures I won't buy anything from them until I can see they've fixed that habit.

I've had this game for awhile and finally got around to playing it, and before I did notice the mixed reviews so wasn't sure how I'd find it. Personally I've been really enjoying the game; there's not much ground breaking aside from the different era paths mentioned by others, and to be fair it took me a few starts to get into the game, but overall I think there's a good balance once you get the hang of the mechanics. The game has "mana points" similar to Imperator Rome when that was first released, however the way they are linked with buildings, improvements and other actions I think does work well. The resource paths to boost cities also works nicely once you get used to it. AI seem quite aggressive even at lower difficulty levels but I've not had any problems in dealing with war so far. Overall I think Millennia is a decent game, I haven't bothered with the expansions but the base game seems enough (unlike plenty of other paradox releases).