DAE Think The Game Gets "Unplayably" Boring About Halfway Through?

My favorite part about Civ games are the early stages, the first 100 or so turns, of founding cities and early horsemen war. At the mid-point of the game when riflemen fortify along boarders and AI are denouncing you left and right, the game gets too boring and I often quit.

TL;DR: Game goes stale at around 100 turns, after everything is explored and boarders established.