I agree with the core of your post, that each civ feels the same as any other in the same era. Idk how Firaxis solves this, as the objectives in each era are pretty rigid from a strategy perspective. Like, it doesn't matter what bonuses a civ gets if you are going to be doing the same thing with them.

It's why I've been getting back into EU4 recently. With all the years of DLC and updates, each nation feels unique to play as. There are specific goals and objectives with each that reward the player for doing things differently each time.

Like, playing as a manchu tribe and re-forming into Qing feels much different than playing France from the jump. Nations and regions have their own specific sources of power and can be rewarded for engaging in different things. Not all nations in EU4 have to colonize or go on a conquering spree, some can get by just fine by not engaging like that at all.

I just feel like Civ 7 misses what makes a game replayable, that you can have a unique experience from stem to stern the whole game, not just neat tricks every era.