One of James Cameron's most insightful ideas (which I heard him talk about in an interview) was that in most sci-fi the planets, societies and life forms tended to be monoliths – every planet containing a single climate, landscape, race of beings, etc.

Those of us who live on Earth of course know that the incredible array of customs, cultures, ways of life and relationships to the world around them can be unrecognisable from one tribe to the next.

It was the reason he depicted the water Navi in Avatar: The Way of Water as being so different to the forest people Jake (Sam Worthington), Neytiri (Zoe Saldana) and the gang are from, and he takes that idea and runs with it here. Avatar: Fire and Ash depicts another tribal group of Navi that live in or around a volcano, whose culture centres around fire and ash (hence the title) because it's their home and who are eeeevil (paler skin, sharper teeth, evil grins, etc).

It picks up right after the events of The Way of Water where one of Jake and Neytiri's kids has been killed in the final battle, and then – it has to be said (like Cameron's other great franchise in The Terminator or the slasher films of the 80s) – it tells the exact same story again, the only difference being that Quaritch (Stephen Lang), in the guise of his new avatar, teams up with Varang (Oona Chaplin) of the Mangkwan, a fearsome tribe who reject the mother goddess Eywa.

It's got Jake and Neytiri plotting for a coming onslaught, their kids (including the human one, Spider) all jostling for a sense of belonging and maturity while calling each other 'bro' so many times I again thought I was watching an urban street gang flick, the whales and their stupid language the Navi can understand and Sam Worthington wheeling between American and Australian accents not just between scenes but occasionally in mid sentence.

It's got Quaritch again gunning for Jake and his family, this time contravening his orders by the military-industrial-complex brass led by General Ardmore (Edie Falco) and suit Selfridge (Giovanni Ribisi), more new Pandoran animals and ecosystems, more diving and swooping on those flying reptile bird things while endlessly shouting 'Wooooh!', etc etc.

To be honest and fair, it didn't irritate me as much as The Way of Water, which was strange because it was such a retread of that movie. It did offer some new battle landscapes like the base/city the humans have established on Pandora, but everything else was the same; fighting in the air, fighting on the water and connecting to the organic nerve network of the planet to ask Eywa to send all the animals to help.

As I write these words it's made $1.2bn after almost a month of release, so it looks from here like it won't be quite the monster smash the last ones were, and with Cameron having said a few times how these films take so much time to make and how old he is – alluding to maybe stopping if they don't remain worldbeating hits – maybe we've seen the last of it?