You can't delete the templates, however you can easily hide the templates via hook.

With this hook, only custom templates will be displayed, making it easier for the editor to find a template.

function atkp__modify_template_list(  $templates, $add_systemdir, $is_searchform ) {
 
     $newtemplates = array();
     
     foreach($templates as $template => $val) {
          if(is_numeric($template))
                $newtemplates[$template] = $val;
     }
     
    return $newtemplates;
}
add_filter( 'atkp_template_list', 'atkp__modify_template_list', 10, 3);