In WordPress, we have what is called as "main query" which points to the global $wp_query object (which is an instance of the WP_Query class), and this main query is run on page load after WordPress parses query arguments from the current URL (or the relevant query for the matching rewrite rule for that URL).
And you should never change/overwrite ...
You can use get_queried_object() to get the static page data, and then do something like so to get the excerpt of the page:
echo get_the_excerpt( get_queried_object() );
// Or to apply filters just as the_excerpt() does:
$excerpt = get_the_excerpt( get_queried_object() );
echo apply_filters( 'the_excerpt', $excerpt );
You don't need functions for this, just look in your theme's template files: For single posts check single.php and for blog archive/categories check archive.php.
Change the <h6> in those php files to <div> or whatever you want. It would be wiser to override them with a child theme so you don't lose your changes in a future update of the theme.