That system does get kind of ridiculous once you get to the contemporary era and nuking a city maxes out the enemy's war support, as does airstriking enemy troops that are in a city. Not that it really matters, because if you've gotten nukes then you've probably already handily won the game and you're just flexing on the other empires at that point. What's really funny is airstriking enemy troops in neutral territory, resulting in a sternly worded letter from the territory's owner because they're still in the early modern and you have nukes and an airforce so they can't do shit.

But then the industrial and contemporary eras are kind of... barely functional as they stand. The only late-game units that actually seem to match the tech disparity you can get are attack helicopters, since they're fast and immune to melee while everything else is just a normal, slow ground unit that has ranged attacks. Late-game ships are absurdly slow and can be outpaced by buffed sailing ships, and the plane mechanics don't work (like you can't merge squads of planes, making it a pain in the ass to organize them since only one squad can be on a tile).