The developers of Millennia have run a Q&A on their official discord, and they are now reporting back the results. Some of the questions relate back to Civ, e.g.
Question: Will the terrain change with ages? Like finding new ores in civ. And are they influenced by the kind of age? Like the age of plague making fresh water more important
Answer: There are Goods that are revealed as the game progresses or when certain Ages are entered into (or certain National Spirits are selected).
Some relate back in general to 4X games, not that specific to Civ, e.g.
Question: Are there “wonders” like in other 4x games i.e. big projects or buildings requiring large investments of resources for a large return, typically embodying some historical wonder like the Colossus of Rhodes or the Library of Alexandria?
Answer: Wonders exists, but in a different way than in other 4X games. A wonder potentially comes from the empire Innovation system, that grants them (the Colossus of Rhodes is one of these). We also have “megaprojects” which are more involved multi-stage constructions – the Space Race is a megaproject, for example.
whereas others go completely into fiction, e.g.
Question: Is there an Alien Civilization/Nation?
Answer: Not a playable one (now).
For the whole Q&A please check here.