I'm trying to change meta description and keywords (I know keywords aren't useful) in Magento CMS pages, but the site is still outputting the sitewide default values. What am I missing?
If There is a CMS page then go to the CMS >> Page >> Add/ edit you find the META tab in that you can add Keywords and Description. and title will come form Page Information >> Page Title.
If you load the product then This will load from the Catalog >> Manage Products >> you find in Meta Information Tab in that.