Mensaje de producto agotado sin gestión de stock

<?php 
function ft_show_stock_level() {
    global $product;

    $out_of_stock = filter_var( $atts['out_of_stock'], FILTER_VALIDATE_BOOLEAN );

    if ( ! is_a( $product, 'WC_Product' ) ) {
        $product = wc_get_product( get_the_ID() );
    }
    if ( ! $product ) {
        return ''; 
    }

    if ( $product && $product->is_type( 'variable' ) ) {
        $available_variations = $product->get_available_variations();
        $total_stock = 0;

        foreach ( $available_variations as $variation ) {
            $variation_obj = new WC_Product_Variation( $variation['variation_id'] );
            if ( $variation_obj->is_in_stock() ) {
                $total_stock++;
            }
        }
        if ( $total_stock === 0 ) {
            return '<p class="font-bold">Producto agotado</p>';
        } else {
            return ''; 
        }
    }
    if ( $product && $product->is_in_stock() ) {
        return ''; 
    } else {
        return '<p class="font-bold">Producto agotado</p>';
    }

    return '';
}
add_shortcode( 'stock_level', 'ft_show_stock_level' );