The Avatar/Pocahontas connection is valid, of course, the story was never the film's strong point, just as we already knew the plot ending of Titanic. Writing is often not about the arrival, or even about what happens during the journey, it's HOW you tell it, and that separates the good writers from bad.
Cameron comes closest to being the Disney of our times. Disney often took a punt on his projects, as he did with Snow White, the first animated feature. He had already gone way over his budget with the film only 3/4 made when he brought his financial backers to a theatre to watch slices of storyboard, line tests, rushes and finished footage spliced together to show how it would look when it was finished. The businessmen were so knocked out they voted with their pockets and advanced Disney the money to finish the film.
Most if not all filmakers have studied Disney, just as they studied Chaplin, Kubrick and Hitchcock, not because of his directional skills, but because of his immense talent for telling the same story again and again and making it look different.
Disney's template was always:
Lone hero (often orphan/displaced royalty) banished to wilderness.
Meets kooky band of followers.
Learns about the 'important' things in life, falls in love,
Faces life-threatening situation, survives,
Returns home to defeat super-villain, reclaim birthright.
Use that template for just about every Disney movie from Snow White to Jungle Book, Little Mermaid, Lion King, whatever and you can see that Cameron was less worried about coming up with original plots than putting a 'sure thing' storyline out there, and re-hashing a Disney plot was the quickest way to get that problem solved.
