If you spot an AI player who is slower than you in the neolithic era, there is a simple way to abuse them. Send scouts (or tribes) to find their territories, then as soon as they settle their capital and your forces are in range of it, declare war and lay siege to it. Then there is nothing the AI can do. They can't lift the siege with their units, because they don't have Organized Warfare. They can't research Organized Warfare, because their only city is under siege. They don't have enough influence to settle a second city. So you just wait several turns until all defenders starve, walk into the city and sign peace next turn. You now have a second city in early ancient era with no influence cost, and it may start with a district or two.

If your enemy survives and settles again, that's great! You can attack them later for another free city or territory, no need to abuse lack of Organized Warfare when they are so far behind. Right now I'm in a humankind difficulty game where I started as Egyptians, took Phoenician and Olmec capitals in the way described above, and two more Olmec cities later. My neolithic era was not stellar, but theirs were worse and that's all I needed. With so much free territory I was already way ahead of everyone else in medieval era.

I consider the unbeatable siege an exploit that needs to be addressed. I think starting war support should be set to 0, so you can't just declare surprise war right away. This is probably not enough, so perhaps armies should be allowed to defend against siege without Organized Warfare.