why is Zoe an "ancient being"

like i know we have normal "non-ancient beings" but Zoe being one just feels so off especially with how childish she is. Like i understand the whole Powerful being that cares more about having fun than doing some all important task and shit. But like if she's god tier like Aurelion Sol it just feels a bit awkward to have her like this idk. I think it mostly just i have been waiting for another Kid champion for a while and to find out she's a god just feels eh. Like Runterra has some mystical shit going on down on the surface of the planet yet anyone with power is full grown adult, ancient being, or Yordle. Annie is the only kid really. I'm not sure on Ekko because he seems like he's around Jinx's age, and Amumu is another "Ancient being" situation. I don't know i just feel like there's a lot of missed opportunities. but Zoe looks interesting as she is now (aside from how unholy her mobility might end up) she looks fun.