We have a WordPress website. If we’ve installed an SEO plugin such as All-in-One SEO pack or Yoast SEO that’s all we need, right?

Unfortunately, no.  While these are great plugins (we use them with many of our clients) they don’t do the SEO work for you. They help ensure that the basic on-page attributes such as your title tag, description tag, body copy, and URL structure contain a target keyword.  However, this isn’t the same as actually running an SEO program. See “adding meta data” above.