[Theme: Gemer] Does Not Remove Shortcodes in Preview Text

So the theme I’m using, Gemer, is rather outdated, and sadly does not remove shortcodes from its excerpts. You can see an example at my website https://tungstengames.com. You can see that the [Caption] Shortcode appears in previews, while the html within the shortcode does get removed.

My theme remains this function,

# Removes tags and trailing dots from excerpt
function dp_clean($excerpt, $substr=0) {
	$string = strip_tags(str_replace('[...]', '...', $excerpt));
	if ($substr>0) {
		$string = substr($string, 0, $substr);
	}
	return $string;
}

which is typically called when it fetches an excerpt, so I’m wondering if theres anyway to implement the strip_shotcodes() function here, or somewhere else that’d fix my problem.
Thank You!