Feather people look like so-called ancient witches, but they don't know what they have done to God, and then they become immortal. It may be that they absorbed the power of many ancient gods, and then got immortal magic and supernatural power. After all, there are many remains of ancient beasts in the territory of the feather people.
Moreover, look ahead, Gu Long's soul can be attached to the skeleton. It can be speculated that the feather man kept so many animal bones, presumably to detain the souls of these animals for his own use. Therefore, Zhao Tuo thinks that their practice is very excessive and unnatural for God.