displayed on pages

function dfi_posttype_page ( $dfi_id, $post_id ) {
  $post = get_post($post_id);
  if ( 'page' === $post->post_type ) {
    return 0; // invalid image id
  }
  return $dfi_id; // the original featured image id
}
add_filter( 'dfi_thumbnail_id', 'dfi_posttype_book', 10, 2 );

I really don’t want the featured images to appear on pages. The code above removes it from everywhere.

no, I didn’t. It was for your convenience, I only want to remove default featured from pages, the above code removes from everywhere.