SharePoint Online Modern page - Cannot create template site

This issue is driving me crazy! 

Why is it that I'm able to create a template on some sites and not others? Is there a way to export a site template via PhP that's easily understood by a novice SharePoint designer with very little coding experience? 

Say the site that I'm trying to export is: https://mysite.sharepoint.com/sites/Intranet/SitePages/Home.aspx

What are all the steps involved in getting this site exported and easily imported on my SharePoint Online site if I can't create a template manually in SharePoint (option does not exist)?