Create a custom get_posts() for use in the genesis_sitemap_output() so you can show only specific categories or show all posts but not ones in the exclude parameter. See https://codex.wordpress.org/Template_Tags/get_posts

for-functions.php

<?php
// don't include

/** ====================================================================================
 
 * get posts for sitemap
 * https://codex.wordpress.org/Template_Tags/get_posts

==================================================================================== **/        
function christina_get_posts_for_sitemap() {

	global $post;
	
	$posts = get_posts('numberposts=50&offset=0&exclude=5,7'); //this example excludes posts 5 and 7
		
	//Examples: 	
	//$sitemap_post_list = get_posts('numberposts=50&offset=0&exclude=1646'); // exclude a post by ID, use commas between all the posts you want to EXCLUDE
	//$sitemap_post_list = get_posts('numberposts=50&offset=0&category=5'); //show only a specific category by ID, use commas between the other ids you want to INCLUDE
		
	$sitemap_post_list = '<ul>';
	
	foreach ( $posts as $post ) :
	  setup_postdata( $post );
	
	$sitemap_post_list = '<ul>';
	
	foreach ( $posts as $post ) :
	  setup_postdata( $post );
	
	  $sitemap_post_list .= '<li>';
	  $sitemap_post_list .= '<a href="' . get_the_permalink() .'">';
	  $sitemap_post_list .= get_the_title();
	  $sitemap_post_list .= '</a>';
	  $sitemap_post_list .= '</li>';
	
	endforeach;
	
	$sitemap_post_list .=  '</ul>';
			
	return $sitemap_post_list;
	
	wp_reset_postdata();
	
	
}