In contrast to the real world where humanity reigned supreme, they were considered as one of the weakest races in this one.
Humans built grand cities on the plains, but just living there highlighted how fragile humanity was.
The open plains were a dangerous terrain. Their enemies were able to easily spot them due to the lack of places to hide in. The reason they had to settle for such a place was their lack of night vision, leg strength and stamina. Since humans were a weak race, they would’ve never been able to build their own society/civilization had they choosen to live in another place
Lots of races were stronger or had a more advanced civilization than humans, but these races didn't dominate the land. They fought against the 8 Kings who attempted to rule over the world, allowing humanity to survive the war. If it wasn’t for this, humanity would have already been eliminated.