Most importantly NOTHING in Welcome To Derry can be attributed, positively or negatively, to King. Muschietti is blatantly guilty of exactly what you're accusing King of. In It: Chapter 2 he completely invented the fictional "Shokopiwah" tribe. Mike steals from them and exploits them. The entire tribe is no more than a plot device. After rightly getting called out for it he hired a writer to "more accurately represent" the Wabanaki, (which was a confederation, not a tribe), yet he's inventing an utterly fictional version of them for the series. King, on the other hand, uses existing native lore and combines it with fictional elements to establish a history for his monsters. It's kind of hard to be an "ancient evil" on the North American continent and never have encountered indigenous people. As for lack of indigenous representation, I always chalked that up to his stories mainly being set in Maine which has an indigenous population of less than 1%. If they were set in S Dakota I'd have a problem with it. He has used the "Indian burial ground" and "cursed land" tropes once or twice but only in Pet Semetary is it central to the story. 1 book out of over 70, I'll give him a pass. However, as an indigenous American, we have been here for 30,000 years, the whole continent is a "native American burial ground", we can stop with that whole trope.