I don't know what people were expecting from a summer blockbuster: Tolstoy meets Roddenberry perhaps?
I wonder why people always say this. Why do people, the audience, themselves allow summer blockbusters to be so empty and brainless?
But it wasn't brainless (and it certainly had heart). Admittedly, it wasn't exactly a high-brow movie. On the other hand, it did deal with the security-liberty paradox, a tiny bit of humanitarian intervention vs non-interference, and a September 11th/Iraq War allegory thrown in for good measure.
Fast and Furious 6 will no doubt be brainless; STID is not.