I'm not sure I have any ideas. I was definitely playing Babylon wrong. Tradition works much better with them, or focus heavily on culture policy and religion. I guess run away civs on another continent are just unstoppable at higher difficulties. I always stay in the game and try to maintain happiness and build up a military to attack them, but it just gets worse every turn. I never actually have a chance to attack. The ideological pressure, the city state stealing, the wonder hogging, world congress stuff, my minister of agriculture, barbarian unrest. All this destroys your science and culture making the gap even larger.
I just need to learn to quit and start over.
I just need to learn to quit and start over.