How do I list custom taxonomy terms without the links?

Can try this:

$terms = get_the_terms ($post->id, 'skills');
if ( !is_wp_error($terms)) : ?>

<?php 
    $skills_links = wp_list_pluck($terms, 'name'); 

    $skills_yo = implode(", ", $skills_links);
    ?>

    <span><?php echo $skills_yo; ?></span>