Without GDPR enabled it's impossible to control a contact’s subscriptions from the individual contact record, or en-mass from contact lists.
The proposed functionality is fairly elementry for marketing software of this calibre:
1. On the individual Contact record make the Communication subscriptions section visible and functional, as it is for GDPR users (described in this knowledgebase article — screenshot below).
2. Make adding contacts in bulk work as described in the same article (see highlighted text in screenshot below). Currently this does not work and workflows have to be created as a hack (see this thread).
