Send message to users with certain field enabled with Message Module

I would like to send/display a message in a block view on user profile when some content type node is created, but only if that user has a certain custom field enabled on their profile.

I have created the message template and used hook_node_insert() to send a message but the problem is it sends this message to all users if I(as an admin user) have the custom field enabled or doesn't if I have it disabled.

My hook looks like this:

function notification_node_insert($node) {
  $ids = \Drupal::entityQuery('user')
    ->condition('field_notify_me_about_new_events', '1')
    ->execute();

  $users = User::loadMultiple($ids);
  foreach ($users as $user) {
    $message = Message::create(['template' => 'new_event', 'uid' => $node->getOwnerId()]);
    $message->set("field_node_ref", 'uid');
    $message->save();
  }
}

The problem with my code is also that the block displays multiple identical messages (one for each iteration).

How would I be able to achieve that only users with the custom field enabled would receive the message?