First, that question was closed because it is asking a very site specific question. It was worded as "What is wrong with my site? Here is a stack trace." Questions both here and at the WordPress Stack Exchange need to be written in a way that can help other people solve similar problems. As it stands, that question would likely get closed even if it were moved. Hence, I closed it rather than moving it.
Second, there are plenty of questions that would be a better fit here, even if they do involve WordPress. The WordPress Stack Exchange is focused on questions about WordPress development and administration. Questions about blogging with WordPress or about SEO for a WordPress site would be better asked here, and should be tagged with wordpress.
The wordpress tag is useful and we shouldn't remove it. Some WordPress questions belong here, but questions relating to WordPress development or administration should be moved to wordpress.stackexchange.com.