As of July 11, 2018, the Facebook connector can still download Page Insights data, but the Post Insights and Page Posts queries return !Error 400. This is partially due to a bug in the Facebook API, and partially due to a change in Facebook’s access policies.
When they fix the bug, you should be able to get posts for pages you own, but not for other pages, even if they are public. Access to other public page content through the API has been terminated.
Mike