Moana 2, a billion-dollar film despite animation industry struggles, is panned as a poorly-structured sequel originally intended as a Disney+ series. The plot involves Moana preventing her people's extinction by finding a lost island and stopping the villain, Nalo (though Nalo is barely seen). The reviewer criticizes the weak plot, repetitive songs, and reliance on slapstick humor, comparing it unfavorably to other Disney sequels. Based on the provided context, the significance of the island Moto Nui in Moana 2 is not explicitly detailed. The provided information focuses on plot points like Moana's quest to find other Pacific Islanders ( ), her encounters with various sea creatures ( ), and the overall narrative structure which is described as a "monster of the week" format ( ). There is mention of Moana's ancestors helping her ( ) and a conflict involving Nalo ( ), but no specific role for Moto Nui is described. Therefore, further information is needed to accurately answer your question about the island's significance in the movie's narrative. Based on the provided context, one new character introduced in Moana 2 is Moana's little sister, described as "so gosh darn adorable" ( ). Another is Matangi, a character banished to live inside a giant clam who helps Moana on her quest by providing guidance and perspective on following rules ( ). The provided information doesn't offer details on other new characters or their specific roles in the story.