Code for unique user visit count on every page WordPress

My guess is that the user must be logged in? If that is the case you can simply store the page hits as metadata doing something like this:

add_shortcode('pagehits', 'showPageHits');

function showPageHits($attributes)
{
  /** @var \WP_Query $wp_query */
  global $wp_query;
  $page = $wp_query->get_queried_object_id();
  if (is_user_logged_in()) {
    $user = wp_get_current_user()->ID;
    $meta = get_user_meta($user, 'pagehits', true) ?: [
      'pages' => [
        $page => 0,
      ],
    ];
    $meta['pages'][$page]++;
    update_user_meta($user, 'pagehits', $meta);
  } else {
    $address = $_SERVER['HTTP_X_FORWARDED_FOR'] ?? $_SERVER['REMOTE_ADDR'];
    $cacheKey = 'pagehits_' . $address;
    $meta = get_transient($cacheKey) ?: [
      'page' => [
        $page => 0,
      ],
    ];
    $meta['pages'][$page]++;
    set_transient($cacheKey, $meta);
  }
  echo sprintf(_n('You have visited this page: %d time', 'You have visited this page: %s times', $meta['pages'][$page]), $meta['pages'][$page]);
}

If the user is not logged in the above will store a transient entry where the key is created based on the clients ip address e.g. pagehits_192.0.0.1.