functions.php

<?php
/**
 * Include autoloader.
 */

$autoloader = __DIR__ . '/vendor/autoload.php';
if (!is_readable($autoloader)) {
    error_log(
        sprintf(
            // translators: 1: Theme name. 2: Composer command. 3: theme directory
            __('%1$s installation is incomplete. Run %2$s within the %3$s directory.', 'my-theme'),
            wp_get_theme('my-theme')->get('Name'),
            '<code>composer install</code>',
            '<code>' . str_replace(ABSPATH, '', __DIR__) . '</code>'
        )
    );
    return;
}
require $autoloader;

/**
 * Initialize classes
 */
array_map(function ($class) {
    call_user_func(["\My\Theme\\$class", 'init']);
}, [
    'Setup',
    'Assets',
    'Widgets',
    'NavMenus',
    'Blocks',
    'Hooks',
    'Customizer',
    'Jetpack',
    'Breadcrumbs',
    'ACF',
]);