No depth? No depth! The whole movie has hidden depth if you look for it. To quote my oh so eloquent friend, Pulp Fiction was about two things, "Sin and Redemption." The characters, different as they are, all commit sins, and those who see the error of their ways are redeemed, and those who did not were not. Jules killed three men. His near death experience changes his life and he ends his criminal ways. Vincent sees this as foolish. He sins without repenting. His drug addiction results in Mia confusing heroin for coke and OD'ing, resulting in her almost dying. He is mean to Butch. On his next assignment he is killed by Butch.
Butch, on the other hand, went back on his word and killed a man in a boxing fight for monetary gain. He is then hit by a car and hurt severely by Marcellus Wallace, who plans to kill him and probably could. But he takes pity on Marcellus when given the chance, and Marcellus gives him a chance at life without the need to look over your shoulder every two minutes.
And this is without mentioning the excellent structure and dialogue of the movie as well. Anybody who thinks this movie is merely a vehicle for swears and racial slurs is a fool.