As for people not seeing it in massive numbers. Look at the overall picture. Every movie is underperforming to some degree this year. The United States is in a serious recession, and it looks like it will take some time to climb out of it. People just don't have the money they did back in 2008.
The critics panning it don't mean squat. Critics panned The Hangover 2, and look how massive it did, and the critics praised Super 8, and look how unmassive it did. Critics themselves are simply not a factor.
The biggest complaints I hear for reasons people don't want to see the film in neck of the woods, #1, is that they don't like how the Transformers looked all the way back from the first movie. #2, lot of people like Megan Fox, and they skipped this one because she's no in it. #3 the sexual tone and nature turns alot of people off. I know, it's a double edge sword with sex is a no no, but violence and carnage is OK, but it's an undeniable fact.