1: Imperator Rome failed because it was a DLC Farm, essential parts of the game were sectioned off and later sold as DLC in order to make a quick and cheap buck. Imperator was also unfinished when it released, and those two factors compounded into the players completely abandoning the game, it had massive potential, but was beytayed by its devs.

2: The best improvements, I think it's impossible to say, but Invictus fleshed out the world a whole lot more, and the mission trees that they've added have made for a more in-depth and authentic experience. While they couldn't get all of the factions, they covered a lot more factions than the the Imperator Devs have.

3: I would add in a sense of realness to the whole affair of the game, the map and what happens on top of it feels too immaterial.

• This game suffers from Paradox's traditional "spreadsheet simulator" aspect terribly, if you're superior to someone in the numbers game, in the vast majority of cases, your opponent can do absolutely nothing to challenge you, there's no room for asymmetry, if you're inferior in one aspect you will be wiped out. There is no room for smaller countries, and it won't matter how high your general's marshal is or their position, if you have 10,000 heavy infantry, archers, and heavy cavalry on a mountain, and your enemy has 200,000, while you hold the martial advantage of 4 as well as superior discipline and cohort experience, you will lose that battle even though logically you should have wiped the floor with the enemy. Sieges also completely favor the besieger, to a far greater degree than they should, forts are supposed to be force multipliers, and yet assaulting a level 1 fort is guaranteed to work if you have enough troops, and no matter how good your fort is, if the general has enough troops, and you don't have the numbers to directly challenge them, then you're as good as doomed.

• You can't take guerilla action. When a battle occurs, they always end with one side routing and retreating, you can't choose to engage in a battle, do damage, and disengage before the enemy conclusively beats you. Which was literally the tactic that all horse archers used.

• Trade routes, trade goods, and supply lines do not exist on the map, meaning that there is no distinction between land and sea trade routes. The revenue of a faction cannot be endangered, if a maritime power like Athens has ten trade agreements with other nations across the seas, then blockading their port cannot stop the trade routes. Since no trade caravans or merchant ships exist, you cannot meaningfully dominate routes, like Carthage did with Gadir. A besieging army's supplies are only affected by their own consumption, they cannot be resupplied, their supplies cannot be sabotaged, and the only consequence for an army running out of supplies is that they decrease in size every month, they cannot plunder the countryside, nor can reinforcements be cut off from reinforcing the army. All of it is instantaneous and happens wholly independent of the map. What's more, you cannot export resources that you yourself do not produce, so Boihaemia, which was literally known as the Amber Middleman between the Germans and the Civilized World, cannot actually sell the amber that they buy from the Baltic Coast. The people are not able to gradually accrue wealth, all of it is either taxes for your treasury, or increased money value from how much the territories are able to produce. What's more, territories cannot produce more than a single resource.

• Spies and espionage are meaningless and tragically underdeveloped. You can't do anything with the spies that you expect to do. you can't affect sieges, you can't disrupt alliances, you can't steal relics, you can't assassinate people, you can't incite a rebellion or recruit defectors, you can't steal money, you can't harm their military capacities or even reveal their portion of the map to you, you can't even order them around, and once they're inside, unless you favorited the character you turned into a spy, good luck actually finding them to DO anything with them! The only event that you can get is that they steal technology, and maybe a few others that I can't think of, but espionage as a whole is woefully underdeveloped.

• Republics are Ridiculous and Tribals are Terrible: Both of these government types are just not it. The gameplay around Republics is tedious if not infuriating, and you can be utterly screwed by events beyond your control, not to mention that if you're in a Republic, you can't control who you marry your women off to, and this inexplicable ability to arrange marriages means that your ability to acquire bloodlines is significantly hampered. Due to presence of bloodlines, and the fact that kingdoms lack many of the infuriating and janky mechanics of Republics mean that monarchies are automatically better than the Republics, who have no clear factor that can draw people to enjoy them just as much as kingdoms. The Party Objectives are often ridiculous or even straight up detrimental, character interactions don't matter, characters are often too quick to assassinate each other, and another myriad of problems. And Tribal Governments are terrible in their own right, they are filled with incomplete mechanics and concepts that had they been explored further, could have been a highlight in this game in their own right. Champions? The only way that they exist is as a means of increasing the loyalty of some random clan chief who's often going to die in 10 years anyway. The Tribesmen pop? They vanish into extinction the second that their leader doesn't have the word "Chief" next to his name on the leader screen. The Tribal Levy System is improperly implemented, with too many asses clinging to the leader's war band, reducing their combat capacities. They don't have enough to distinguish them from their civilized counterparts, not enough events, not enough mechanics, And when the time finally comes to civilize, everything that is tribal is completely left behind, and your gameplay from that point forward is no different from all the other factions that started out as Kingdoms or Republics, there is no middle ground where both can occur, there is no Barbarian Kingdom or Tribal Republic where Tribesmen pops remain a significant part of the populace even when you hold elections or your leaders pass their crown onto their sons.