Summary

Currently, it's impossible for an organization admin to bulk manage their users' marketing email subscriptions.

If a user wants to change their subscriptions for marketing emails, they have to do it through their profile individually

https://id.atlassian.com/manage-profile/email 

To manage marketing emails, visit the email preferences center.

Suggestion

Allow admins to set default settings for the email preferences center, or to manage their users; settings.