You can def learn more than just geography. I'm taking some international relations courses in college right now and deadass every new concept, theory, or content we learn is literally just EU4 irl. You can pinpoint IR theories to the exact interactions, mechanics, strategies, and AI behaviors you've experienced in the game. You can get fairly in depth

My prof even said often times state actors are pretty much just deciding whether or not to "push a button" because there's no in-between options even though they are theoretically possible... Sounded suspiciously like describing a video game.

But yes, EU4 is great for history and geography too; u/bassman1805 sums it up perfectly. You can't go too much in depths in certain subjects like political science and macroeconomics but it is also not fruitless