I did see it. Great anime by Hayao Miyazaki and Studio Ghibli.
Now, first of all, what version did you watch it? There's the original version, and there's the american version called "Warriors of the Wind". The american version butchers about 20 minutes of the film, alters the plotline and changes the dialogue - it is so bad, compared to the original version, that Miyazaki said he wanted to burn every copy (like GL and the holyday special). Was there a scene in which Nausicaa dreams about her past while being engulfed by the Ohm's tentacles? If so, congratulations, you've watched the original version.
I think you've missed the point. Earth was destroyed by men, but even so, Earth managed to cope with that destruction and create a perfect "balance" of it's natural resources, animals, and the polution. At what cost? Mankind was confined to small villages, always afraid of the polution madness it has created. I think it's a great environmentalist film, it's just that it's upbeat and positive about the future.
If you want to see a good environmentalist anime, watch "Future Boy Conan" (a 1978 anime masterpiece also by Hayao Miyazaki).
By the way, the scene with the giant warrior - my favorite in that anime - was animated by Hideaki Anno, who, 11 years later, created and directed Neon Genesis Evangelion. So I guess I can see where part of his inspiration for Evangelion came from...