According to the new change introduced in Confluence 9.1 supporting the feature request CONFSERVER-45898, pages are now getting created in new format which includes (space key, page ID, and page title for better readability).

In order to use old Page creation URL format we need to enable confluence.readable.url.disable under darkfeature. This will change all the pages urls to new format including old pages. If we search with old page URL, currently we are getting 404 error. It will be helpful if we can add some feature which will help to redirect pages to actual page URLs even if we access the page with old page URLs(without space key, page ID)