Seeing as it’s in a loop, you should be able to check against the type of post, and only add it to that type.
function add_rating_html( $title) {
if ( is_front_page() && 'post' === get_post_type() ) {
$out = "Rating: 5";
$title .= $out;
}
return $title;
}
add_filter( 'the_title', 'add_rating_html', 1 );
There’s probably a better way to do it by hooking on to the specific widget, but I’m no expert with how Elementor works