as for the few technologies, that's inevitable because all stuff like feudalism or liberalism were put in the civics tree. I think what makes the eras feel like they're zipping fast is that there are more of them - especially in the end, the progression industrial - modern - atomic - information is pretty fast. Makes some sense, as people born in the modern era are still alive today in the information era.
Anyway, I am more annyoed by the lack of new advanced civilian buildings in the information and atomic eras. I mean, it feels like all our technological improvements since the end of the first world war were only good for getting bigger guns. but this is going offtopic. probably the optimal solution will be to add just a bit more crosslinking in the right places. btw, I think the cartography thing is also somewhat justified, as polinesian people had cartography (a primitive version, but they could use it to locate the proverbial pin in the whole pacific ocean) without having virtually anything else. We think the current tech tree is unrealistic, but it's actually reality that is more surprising.