DLC unbalance in difficulty curve early vs mid game

[mdeha004]

Why is it that after a hundred years or so any decisions you make in the game don't affect the DLC content much? It seems like difficulty is concentrated towards the 14th century and after that you can snowball. It seems like most people get bored in the middle of the game because there isn't much more that challenges them. Sure they complain about colonization sucking up pops but if they played till 1800 they'd just get those pops back due to natural growth usually. I don't know of too many games that make the early game challenging and the mid game trivial if you stack things up right.