EU Rome is 11 years old. It is actually a really fun game if you can get past the dated bullshit. There's a lot of unique mechanics, specifically for Rome, Carthage, and the Hellenic factions that are never reused in any later Paradox games. For instance, Rome has a really, REALLY detailed Senate mechanic where you have to balance the factions against one another, and then you have to balance the Senate factions with army generals, because if a Senate faction doesn't have equal representation among military leadership, they will revolt. Units also aren't interchangeable, because over time units will develop loyalty to their specific general instead of Rome, and will revolt if you remove their general from command or try to move them to a new army.
Like I said, a lot of really really interesting and detailed mechanics that have just never been used since.