How to update custom fields when post is published?

I’ve created two custom fields on the post edit screen using the ACF Pro plugin. If the fields are empty, I want to set the current user as both the field’s value when the user clicks Publish button.

This is how I’m calling the function

add_action('transition_post_status', [$this, 'setOwnerAssignee'], 10, 3);

This is the setOwnerAssignee function

public function setOwnerAssignee($new_status, $old_status, $post)
{
    if ($new_status == 'publish' && $old_status != 'publish' && $post->post_type == 'post') {
        $current_user = strval(get_current_user_id());
        update_post_meta($post->ID, 'owner', $current_user, '');
        update_post_meta($post->ID, 'assigned', $current_user, '');
        // wp_die('die');
    }
}

I checked in PHPMyAdmin and the function properly sets the values if I use the wp_die in the end or if I remove the if condition. But it isn’t working without that.

I’m fairly new to WordPress development so I might be doing something silly.