I think that is important...
Basic Science buildings get boosts from Resources...in ALL 3 Ages
Basic Food buidings get boosts from Water...in ALL 3 Ages
Culture buildings get boosts from the same things Happiness buildings do...in ALL 3 Ages
You get resources from other civs by building a Merchant and getting it to a Trade route.... in ALL 3 AGES
..what if Merchants were for Antiquity and
in Exploration, You got resources from other civs or your distant Lands settlements from Treasure Convoys.
You want Iron from China or your new Colony in America... a Treasure Convoy has to move to one of your Homeland cities.. (the Iron doesn't count for points, but the Spices might)
...In Modern, Trade has a different model.. it has to connect to a Factory to supply that Factory.... or not just the exact same thing as Ancient but the Merchant gets to Teleport.
Specialists have a base of 2 Culture and 2 Science with +50% adjacency in Every Age
Now here at least Modern has big Ideology based boosts and Exploration enhances the Adjacency,... but it could be differentiated further.
etc....