those are pages which do not have the Featured Image, Excerpt or Post Meta.
Do you want to remove them from the Search results ? Or do you want to display additional page content in the Search results ?
That will provide the Excerpt meta field on Pages. Which will be displayed in Search results.
2. You can add a Featured Image to your Pages and choose not to display them using the Disable Elements meta. This will remove it from the single page but should still display them in your search results: