Yes. Young people who are going to become the next leader are expected to grow up to be a great leader. That's hardly a rip-off, as that is the case in every movie where a young to-be leader is growing up. And in every real life case like that. That's just normal. As far as Mufasa coming back vs Tala coming back, they were done rather differently (Mufasa being his father and the previous leader telling him to go back and be the leader, vs her grandmother who was not a leader telling her to not go back and continue following her dream). But yes, I'll give you the similarity that their visited by a family member as a ghost. Hardly a similarity, but I'll give you that one. And, as the poster above said, Simba wants to just lie around and do nothing as a leader. Moana strives to be a great leader, and only abandons her post to do exactly what a leader would do: save the island. So Simba abandons his duty, while Moana travels across the sea to complete hers.
Moana doesn't feel she's a disappointment. She is disappointed herself that she's discouraged from following her dream, while Mulan feels like a disappointment for failing to be a girly girl. Her father is called to battle, she wants to take his place. Moana is called to her mission. So, they both have a mission and they succeed. I'm not even conceding that, as that's a ridiculously broad generalization.
Ariel betrays her father because she's "in love" with a boy she's never met, so goes to a sea witch to be changed into something she's not to have a chance with him. Moana doesn't feel out of place, but just wants to have a hobby that her father disapproves of. When that hobby is shared by her ancestors and is needed to save the island, she decides to do what she must for her village. That's not similar.
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