This page  essentially is just a view on a list  - nothing more than that. If you go to Customize List from the sites  page, you will see "Division", "Region" and "Spotlight Site" as added columns. You can delete or change all of these. There are two web parts on the Summary view that control what is displayed here.

Also, the "All Items" view will actually list all sites and you can change this to be the default  view.

Please note, though, that the Sites Directory only lists  those sites that have been REGISTERED in the directory either at the time of creation or by having a link added. There is no out-of-the-box functionality to automatically list each and every site created.