No Mo Tags

no-tags.php

// This is not fully tested :)

function bww_disable_tags_support() {
    // Unregister tags from posts
    unregister_taxonomy_for_object_type('post_tag', 'post');
    
    // Remove tags from post types (including custom post types)
    foreach (get_post_types() as $post_type) {
        unregister_taxonomy_for_object_type('post_tag', $post_type);
    }
}
add_action('init', 'bww_disable_tags_support');

// Remove tags from admin menus
function bww_remove_tags_admin_menu() {
    remove_menu_page('edit-tags.php?taxonomy=post_tag');
}
add_action('admin_menu', 'bww_remove_tags_admin_menu');

// Remove tags from quick edit
function bww_remove_quick_edit_tags($actions) {
    if (isset($actions['inline hide-if-no-js'])) {
        unset($actions['inline hide-if-no-js']);
    }
    return $actions;
}
add_filter('post_row_actions', 'bww_remove_quick_edit_tags', 10, 2);