What is the alternative to “ when it comes to calling Media (image) files in the ‘attachment.php’ file?

Calling the_content from within attachment.php will bring you the Attachment Description.

Put the code below on your page and see what you can get from within attachment.php file:

while ( have_posts() ) : the_post();

    /**
     * @link    https://codex.wordpress.org/Function_Reference/wp_get_attachment_metadata#Related
     */
    $data = array(
        get_the_ID(), // Gets att ID.
        get_permalink(), // Gets att page link.
        get_the_title(), // Gets att title.
        get_the_content(), // Gets att description.
        wp_get_attachment_metadata(), // Gets att metadata.
    );

    var_dump( $data );

endwhile;

Also, you might want to take a look at https://codex.wordpress.org/Function_Reference/wp_get_attachment_metadata#Related and see other functions that will perhaps be useful for you.