Someone or something that is vacuous is (1) devoid of matter, empty; or (2) lacking intelligence, inane. The conventional definition of vapid is lacking liveliness. It’s a synonym of dull. So to use vapid to insult someone’s intelligence is not in keeping with the traditional definition of the word. Vacuous would make more sense. Nevertheless, if you Google “vapid,” you’ll see that many people use it to mean stupid.
The improbable plot ends up being almost the only point of interest in this vapid and hopelessly unoriginal first person shooter. [Metro]
After all, it stood to reason that a live band would inject some energy into an otherwise vapid crowd. [Columbus Other Paper]
Today’s stars are skinny, vacuous identikits, whereas Jane Russell was a real woman. [Telegraph]
I savour the peace, the vast and vacuous silence interrupted only by the flap of prayer flags in the wind. [Toronto Star]