my_get_shortcode_atts() - see https://wordpress.stackexchange.com/a/406679/137402 for details

functions.php

<?php
/*
 * Get the attributes, if any, of the first shortcode with the tag $shortcode_id,
 * in the current post.
 *
 * @param string $shortcode_id Shortcode tag like "foo", foo_bar or my-shortcode.
 * @return array|string|false Returns an array of attributes if the shortcode is found, and
 *                            it has one or more attributes, e.g. array( 'att1' => 'value' ).
 *                            '' (i.e. empty string) is returned if there are no attributes.
 */
function my_get_shortcode_atts( $shortcode_id ) {
	// get the content before the loop
	// Honestly though, I (Sally) would use a $content or $text, or $post parameter..
	// and FYI, get_queried_object() can be used to target the current page you're on.

	$fst_content = get_the_content( null, false, get_post() );

	if ( ! $fst_content ) {
		return false;
	}

	// retrieve cached attributes, if any
	$cache_key      = 'shortcode_atts-' . md5( "$shortcode_id:$fst_content" );
	$shortcode_atts = wp_cache_get( $cache_key );

	if ( is_array( $shortcode_atts ) ) {
		// return the 1st array item, if set
		return $shortcode_atts[0] ?? false;
	}

	// extract shortcode attributes - $matches[3] is the attributes string, whereas
	// $matches[2] is the shortcode tag
	preg_match_all( '/' . get_shortcode_regex() . '/s', $fst_content , $matches );

	$shortcode_atts = array();

	if ( isset( $matches[2] ) ) {
		foreach ( (array) $matches[2] as $key => $value ) {
			if ( $shortcode_id === $value ) {
				$shortcode_atts[] = shortcode_parse_atts( $matches[3][ $key ] );
			}
		}

		// cache all the attributes from $matches[3]
		wp_cache_set( $cache_key, $shortcode_atts );
	}

	// return the 1st array item, if set
	return $shortcode_atts[0] ?? false;
}