This video essay by CosmicCloud covers most everything i love about Splatoon worldbuilding. There is no good and evil, only perspectives, and that the human legacy is creation of art.
It is long, but well organized with chapters. Recommended!
I particularly loved the presentation of how Splatoon (1) gives us the inkling perspective of carefree ignorance while offering a world in which two sides paint the other in propaganda. It overtly explain the themes but allows them to naturally exist in its world.
Additionally, this video made me appreciate the reveal in Splatoon 3's After Alterna of human's connection to Inkling evolution. At first, I didn't accept it, but I think now it supports the intention of Splatoon. Despite featuring the end of humans, Splatoon isn't nihilistic and has a great message about the power of art.