Thanks for your feedback. We're working on some new signup form options for the near future and will be sure to share more detail here when we have it. Although we no longer directly offer the Wordpress.org plugin it is still available on Wordpress.org directly. Please note, this isn't a Constant Contact product so you would want to use it at your own risk. This allows you to add signup forms to your website (sidebar or content) and configure how they look.
The only options besides this are to use an API or the basic JMML form. Thanks again for your post!