When you create a communication site, you can add pages using a template to help you get started.
Some functionality is introduced gradually to organizations that have opted in to the Targeted release program. This means that you may not yet see this feature or it may look different than what is described in the help articles.
You must be a site owner or SharePoint administrator to add pages.
If you are a site owner but you are unable to add a page, your administrator may have turned off the ability to do so.