Unpublishing page delete automatically from site pages library using MS Flow

Or if you mean you only use a site for publishing news and want to remove news pages that get unpublished etc. you could also do a flow to delete files that a. have a first published date and b. promoted state = 0, this will remove pages that used to be news.

You could this by means of a Flow that runs on a schedule and checks any draft stored in the Site Pages Document Library (You could use the SPO REST API for this purpose) and then delete each page