Nearly everyone would go to be entertained. The pseudo-intellectual, snobbish, retarded critics alluded to by ctizenkhan would also aim to be entertained by even the 'worst' movie, but by a perceived gain in status, while they may not appreciate the positive points. Silly emotional reasons. A purely non-intellectual approach is just as foolish.
Not getting too hung up on flaws is a good thing, but that doesn't mean one shouldn't think. I haven't seem F&F, but I would guess much of the acting is terrible, the stunts impossible and the plot painfully bad. But that doesn't mean you can't have fun watching it, while acknowledging the flaws. Free critical analysis and greater knowledge should make film even more enjoyable if one is reasonable. If the focus point is great racing, then I can understand annoyance with wasting time on a mess of a plot. For this style of film they should just get to the action!
Coincidentally, I just saw Harry Potter and the Goblet of Fire with my family and enjoyed it as a darker kids' film. I was annoyed by the plot inconsistencies but I haven't read the book to compare. The cast was good, but poorly directed and I expected a strongly narrative driven film to make more sense. Gambon's use of three different accents was also very unprofessional (Secret twist: Dumbledore has a split personality!) They haven't heard of continuity it seems.
