The concept of SEO page theme is not difficult to understand. Site theme is the same concept taken to the level of a site.
Download the page and all linked to documents and use that information to determine what the page is about. One does not need to look to hard to see that what needs to be changed to optimize a wordpress blog for SEO that each article needs to be associated with a category and links to categories not related to the subject matter need to be delinked from that page.
And category pages need to have hand selected links to other categories that are related. For example SEO does not have anything to do with music. The ability to change php code exists for wordpress only when it is installed on one’s own host.
Some blogs by the nature of the content they cover may not need any changes. One also does not nessary want a perfect score – there is such a thing as over optimized.