Every movie has 4,5 points in which,movie have to be equally and balanced,like story graphics,sound,climax etc.
These three four points in avatar was not balanced for example the story was not that much great,,just a very simple movie,which doesn't make audience shocked,and there wasn't an extraordinary sound i.e. bgm,and climax was not that great.
Another point according to me is we expected too much from the director bcz he's has big name in industry,,and we think that he made great movies and audience can't expect an average story movie,,like literally rajamouli's rrr was much more epic than this,,this is not like fanboy type review but I think that if u see movie correctly you'll find these points correct,,i guess ,,plz tell me if I'm wrong, thanks.