Customizing RSS Feed

Currently, my wordpress blog RSS only syndicates Title, Permalink and comments (the default fields in ‘feed-rss2.php’):

<item>
		<title><?php the_title_rss() ?></title>
		<link><?php the_permalink_rss() ?></link>
		<comments><?php comments_link_feed(); ?></comments>
		<pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_post_time('Y-m-d H:i:s', true), false); ?></pubDate>
		<dc:creator><?php the_author() ?></dc:creator>
		<?php the_category_rss() ?>

		<guid isPermaLink="false"><?php the_guid(); ?></guid>
<?php if (get_option('rss_use_excerpt')) : ?>
		<description><![CDATA[<?php the_excerpt_rss() ?>]]></description>
<?php else : ?>
		<description><![CDATA[<?php the_excerpt_rss() ?>]]></description>
	<?php if ( strlen( $post->post_content ) > 0 ) : ?>
		<content:encoded><![CDATA[<?php the_content_feed('rss2') ?>]]></content:encoded>
	<?php else : ?>
		<content:encoded><![CDATA[<?php the_excerpt_rss() ?>]]></content:encoded>
	<?php endif; ?>
<?php endif; ?>
		<wfw:commentRss><?php echo esc_url( get_post_comments_feed_link(null, 'rss2') ); ?></wfw:commentRss>
		<slash:comments><?php echo get_comments_number(); ?></slash:comments>
<?php rss_enclosure(); ?>
	<?php do_action('rss2_item'); ?>
	</item>

I want my feed to sydicate title, link, tags, excerpt, custom field (image) and category. Based on Codex, it seems I would simply add the templates provided (https://codex.www.ads-software.com/Customizing_Feeds). But this doesn’t seem to change anything

<item>
		<title><?php the_title_rss() ?></title>
		<link><?php the_permalink_rss() ?></link>
		<tags><?php the_tags_rss(); ?></tags>
		<image><?php the_image_rss(); ?></image>
		<pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_post_time('Y-m-d H:i:s', true), false); ?></pubDate>
		<dc:creator><?php the_author() ?></dc:creator>
		<?php the_category_rss() ?>

		<guid isPermaLink="false"><?php the_guid(); ?></guid>
<?php if (get_option('rss_use_excerpt')) : ?>
		<description><![CDATA[<?php the_excerpt_rss() ?>]]></description>
<?php else : ?>
		<description><![CDATA[<?php the_excerpt_rss() ?>]]></description>
	<?php if ( strlen( $post->post_content ) > 0 ) : ?>
		<content:encoded><![CDATA[<?php the_content_feed('rss2') ?>]]></content:encoded>
	<?php else : ?>
		<content:encoded><![CDATA[<?php the_excerpt_rss() ?>]]></content:encoded>
	<?php endif; ?>
<?php endif; ?>
		<wfw:commentRss><?php echo esc_url( get_post_comments_feed_link(null, 'rss2') ); ?></wfw:commentRss>
		<slash:comments><?php echo get_comments_number(); ?></slash:comments>
<?php rss_enclosure(); ?>
	<?php do_action('rss2_item'); ?>
	</item>

What am I doing wrong?