Just to regurgitate something I mentioned in the unpopular movie opinions thread;
With respect; the argument that Avatar follows similar plot threads to Pocahontas and Dances With Wolves is a weak point and irrelevant for me. People will whine and moan about how it "rips off" other stories, like Pocahontas, Dances with Wolves, Fern Gully: The Last Rainforest, The Last Samurai, etc. Here's a question those decriers climb over one another to avoid; how can all those other films work, but not this one? Is there a magic limit that was reached where stories like this cease to function?
This is a really interesting question. Lots of depth to it. I'm glad you asked it because the types of responses would vary and they would all have some reasonable points to them.
My take is the the best way to see basic writers convention is to watch pilot episodes of TV shows. Most of them are not great at all. But they have to check off a ton of boxes to drive the audience into the complexity of a story that's already mostly unfolded in the lives of the main characters in progress.
It should say something that now when a "prestige" TV series drops now, it's rarely just one episode. Often it's 2-3 episodes that form a type of multi-pilot because there is so much ground to cover.
So for classic storytelling, i.e. the "Hero's Journey", in order for a young upstart to transition from naive, foolish and reckless into competent and wise, the older mentor character has to die. In The Godfather, clearly Don Vito and Sonny have to die at some point for Michael to rise into power and develop. Same for the Lion King, the foolish son and then Mufasa. Same for Star Wars, Obi Wan had to bite it for Luke to be forced to venture out alone and untethered so he could grow as a person and as a leader.
I consider Slumdog Millionaire to be a brilliant film. But if you break it down, it's just a live action fairy tale. It doesn't mean it can't move an audience and tell a good story, but the themes inside are timeless.
James Cameron stays in his wheelhouse, he sticks to very battle tested fundamental storytelling, he infuses his own scripts, often with horrible dialogue, but he knows how to give spectacle and adventure. It would be unfair to ask Cameron to do what Spielberg does ( i.e. gentle audience emotional manipulation)
Feature films have a limited amount of time, they need to hit certain standard check boxes for basic writing convention, thus most of what people see is usually predictable. I know what pizza tastes like, it doesn't stop me from loving it if I eat another slice of really good pizza.
I suspect a lot of criticism that Cameron gets is that it's expected at this point that his films will be ground breaking with every new release. He staggers his films with big gaps, he's extremely arrogant, and he's managed to surpass expectations more often than not. Where I figured out Cameron is a good storyteller was not Titanic nor Avatar nor Terminator, it was True Lies. That film really highlighted most of the best elements of what Cameron can bring to the screen. He'd probably be a great filmmaker for comedy, but he's just too arrogant to do anything else but grand spectacle.
I believe most people overestimate complaints when it comes to mass entertainment. A handful of people saying horrible things to Rose Marie Tran doesn't mean the entire Star Wars fanbase are full of terrorists and hateful people. Personally I think most people enjoy Cameron's films and leave it there. He's not Kurosawa, but he's not trying to be. Cameron's films are like eating Taco Bell for most people. In your mouth one day, and out the other side by the next morning.