I believe the point is that Patrick Batemen isn't cool or interesting at all: he's physically fit and affluent, which people mistake for being cool, but as a person he's completely vapid and obsessed with status symbols and what other people have to say about them, hence the constant cutaways to bizarre monologues about fashion, or food, or pop culture that are all completely empty of any substance when looked at beyond the most superficial level. The only original thoughts he has are ways of saying literally nothing on a topic while giving the appearance that he's made some insightful comment, and everything else is just repetition of critics or ads he's read.

And that's him as a person even before you get into the "he compulsively kills people for fun or over perceived slights," stuff.