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
Or if you mean you only use a site for publishing news and want to remove news pages that get unpublished etc.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.