you’ve specified a meta key, but not a value
$new_args = [
'post_type' => 'news',
'post_status' => 'publish',
'fields' => 'ids',
'posts_per_page' => '5',
'meta_key' => 'is_featured',
'meta_value' => '1',
'orderby' => 'meta_value_num', // not sure that this does
'order' => 'desc'
];
$news = new WP_Query($new_args);
Either that or you need to use a meta_query parameter. https://codex.wordpress.org/Class_Reference/WP_Query#Custom_Field_Parameters. You need to test for the value and you need to test that the value exists. See the “compare” argument.
'meta_query' => array(
array(
'key' => 'is_featured',
'compare' => 'EXISTS'
),
array(
'key' => 'is_featured',
'value' => '1'
),
),
