Why was the novel's strongest demon beast system useless in the immortal world?

The novel's strongest demon beast system was a fictional novel setting. The specific plot and background were not understood, so it was impossible to give an accurate answer. But generally speaking, the system that appeared in novels was usually to promote the development of the story or to provide more help and convenience to the protagonist. If the system in the novel's Strongest Demon Beast System worked in the Immortal World, it might be because the various immortal techniques and spells in the Immortal World were more mature and perfect, and the system could not provide enough help. Or because the characters in the Immortal World had reached a very high realm and no longer needed the support of the system. However, no matter what the reason was, the system in the novel was usually an important character that could provide more help and convenience to the protagonist to promote the development of the story. Therefore, the readers could understand and imagine the function and significance of the system in the novel according to their own preferences and imaginations.