Why upgrade to WP WooCommerce Mailchimp Pro instead of using the free plugin?
The free WP WooCommerce Mailchimp plugin subscribes every customer to one Mailchimp list; upgrading to WP WooCommerce Mailchimp Pro is worth it once you want to segment customers by product with lists, groups, and tags, gate Mailchimp membership to active WooCommerce Subscriptions, or meet double opt-in requirements for international compliance, none of which the free version does.