A message about evil corporations doesn't need to be set on Earth - just look at the Trade federation 
That one at least had less obvious "the pure and innocent natives are awesome for living in harmony with nature...because their nature works in a way that naturally gives them advantages similar to what humans need to use modern technology to achieve" idiocy. That's what I'm talking about with Avatar: Yes, Avatar shows that an alien people who can psychically link with "nature" can achieve dominance and stewardship of it in a 100% non-invasive way (or at least, deceive themselves that they're being non-invasive, as stewardship ALWAYS involves some level of invasion as it involves changing the "natural" order to one that is more healthy for the system overall through intelligent guidance).
In fact, in order to make the point that Evil Humans are "ruining everything" with their Evil Corporate Greed, James Cameron had to create, in essence,
God (of Pandora, at least) as a being that guides things, so that the Evil Corporation could attack
God.
A bit of a strange thing for a movement that usually decries belief in God as part of what makes the Judeo-Christian America, run by Evil Corporations, so evil.
Or even further before that, Nausicaa, which I think did the environmental thing even better than Mononoke, but that could just be my personal preference.
Naussica also had some silliness, but it was much, much better done. Especially if you, I understand, read the manga, which details how nature can, if nurtured properly, cleanse itself of pollutants.
Personally, I tend to find the environmentalist movement to be two things: a front for stealth communists (look at how just about everything that is somehow harmful to the environment according to these movements is capitalist in nature, and how things they support as "eco-friendly" suddenly become the next destroyer of the environment when somebody finds a way to make them work profitably and spread it to mainstream use), or a perverse narcissism. How narcissism? Think about it: Man is so almighty and powerful that we can utterly destroy the environment of an entire world, when we occuply less than 20% of it. And most of our occupation thereof is concentrated in an even smaller area, with a ridiculously thin spread around the rest of the space. And yet, we can destroy it. And, further, environmentalists believe that they, through their actions (which rarely actually impede
their lives, even though they demand activities or restrictions thereof that would impede others' greatly),
save the world. How important that makes them! How righteous! How noble! How powerful! Bow down before these tiny gods, who hold in their hands the salvation or destruction of the Earth!
No, they don't put it in those words, but the hysteria associated with some of the pushes, and the images of how much we "change" the world by just not doing as these prophets of global desolation command in all their fiction, does tell that same tale.
(And no, not all who believe in that false religion are fanatics or preachers; many are just swept up in it. But I do wish people would critically examine the claims and consider the motives of the claimants; ever notice how environmentalist leaders get very wealthy selling the cure for the ailment, and often at government expense that they persuaded people had to happen?)
