You seem to be the only person here that "gets it".
Because the park wasn't built by the ancient Waturi people, the temples, which are now ruins, were.
The park is supposed to be an ultra modern hi-tech luxury resort built by the descendants of the ancient Waturi civilization rooted in their beliefs and customs that " Water is Life".
The theme isn't that it was a magically built water playground the ancients stumbled upon. The theme isn't that the ancients discovered a water oasis and they built a rickety bamboo water park that the locals have kept up for eons. The theme is the modern descendants of the Waturi people have decided to cash in on their ancient beliefs and package it for rich latte sippin', craft beer, craft cocktail, craft taco, well basically craft anything consuming, tiki lovin' hipsters. Trust me, Chloe likes the resort style lazy river over the icky dirty river over at the other place. It just goes better with the luxury cabanas and the concierge.