How to properly use the function.php custom_rewrite_rule()

I'm using WordPress and I have added this function to the functions.php in my theme (the basic twentyone):

function custom_rewrite_rule() {
    add_rewrite_rule('^profile/([^/]+)/(\d+)/?', 'index.php?page_id=104&name=$matches[1]&age=$matches[2]', 'top');
    flush_rewrite_rules(); // Flush rewrite rules to test the changes immediately
}
add_action('init', 'custom_rewrite_rule');

function display_profile_content() {
    $name = sanitize_text_field(get_query_var('name'));
    $age = intval(get_query_var('age'));

    echo 'Name: ' . $name . '<br>';
    echo 'Age: ' . $age . '<br>';
}
add_shortcode('profile_content', 'display_profile_content');

</code>

In the specific page I added correctly the shortcode and my intent would be that for example if go to

Website.com/page/Poul/21

It should show:

> Name: Poul
Age: 21

but whatever I put in the URL it always display:

> Name: profile
Age:0

Troubleshooting so far:

I have saved the permalink page to flush the cache.
Disabled all plugins
changed theme to this basic one,
but nothing seems to work.

How can I do?

The WP_Query does not allow any url parameters, it has list of whitelisted parameters, you can change those parameters using the hook query_vars.

Link to query_vars

Now in order to make it Work like this.

function custom_rewrite_rule() {
	add_rewrite_rule('^profile\/([^/]+)\/(\d+)\/?', 'index.php?name=$matches[1]&age=$matches[2]', 'top');
	flush_rewrite_rules(); // Flush rewrite rules to test the changes immediately
}
add_action('init', 'custom_rewrite_rule');

add_filter( 'query_vars', function( $query_vars ) {
	$query_vars[] = 'age';
	return $query_vars;
} );
function display_profile_content() {
	global $wp_query;
	$name = sanitize_text_field(get_query_var('name'));
	$age = intval(get_query_var('age'));
	echo '<pre>';
	var_dump( $wp_query );
	echo '</pre>';

	echo 'Name: ' . $name . '<br>';
	echo 'Age: ' . $age . '<br>';
}
add_shortcode('profile_content', 'display_profile_content');

Also you might have misunderstood your regex, so rewrite_rules takes the profiles/{name}/{age}

so your URL, that works would be Website.com/profile/Poul/21

You can test this out in the index.php of your theme by adding this code.

do_shortcode('[profile_content]');