I’m no fan of mailchimp (for e-commerce customers I recommend Klaviyo) but Shopify+ is hell to work with. I haven’t had as much grief with a platform as I’ve had building e-commerce stores on Shopify (and I come from Magento). For the price of plus, you get practically nothing. Clients ask me incredulously why they don’t have something as basic as Wishlist support or access to custom fields inside their product pages. Shopify’s own sync tool for dealing with multiple stores doesn’t sync much and their answer to the admin hell of managing multiple stores is to give us a single login and a store selector. For everything else well there’s an app for that.
Yes there’s an API. Yes you can build apps. But that’s an investment and at that point you might as well build something on Woocommerce or Magento. Yes you have to maintain a server and updates on the other platforms but you’ll need that for Shopify anyway. If you want to roll your own Wishlist app (you’ll want to when you see what’s on offer from the shopify store) you’ll need a server, a database - the architecture that Shopify says you don’t need to begin with.