Been playing Millenia, and recently reviewed it on Steam.
There is a good game somewhere in Millenia. It has quite a few good concepts. The multiple currencies (Warfare, Wealth, Engineering, etc) is compelling. However, the Barbarian spam is horrendous. You need multiple armies to keep the barbarians in check, all of which costs Wealth. Oh, you do not have resources that helps you generate Wealth, Oh Well! Too Bad! The Barbarians do not go after the AI's towns, yet I have lost games because a wave of Barbs knock out my city, even when guarded. "Well, you should have built defenses!" True, but the AI should have to build defenses as well. But they do not have to. Have not seen an AI civ get knocked out by Barbs. They will attack an AI's troops, but only if they can not reach your troops. Barbs are basically another civ that is primarily focused on the player.
Some other issues..
Many of the resources are weak.
Gross imbalances between National Spirits. Some are simply way stronger.
Difficulty in gaining some currencies, primarily Engineering and Diplomacy, see National Spirits.
The game tries to force you to be militaristic, since AI civs will forward settle you hard, especially since they do not have to deal with the Barbs like the player does.
As I said, the game has great potential. I simply do not recommend the game in its current state. As the game gets refined, I will be more than happy to change my review.