Adobe will not further enhance this capability (Managing Leads and Lists).
Adobe's recommendation is to leverage Adobe Campaign and the integration to AEM.
Users can be asked to subscribe to Email Service Provider's mailing lists with the help of the Form component used on an AEM web page. To prepare an AEM page with a sign-up form for subscription to your e-mail service mailing lists, you must apply the corresponding service configuration to the AEM page that the potential subscriber will visit.
See Managing Subscriptions in the classic user interface for more detailed descriptions of how to manage your subscriptions.