Context
Enterprise organization admins have the ability to deny the creation of new sites by using product request settings to require admin review.

That being said, it is not possible to prevent non-administrative users from accessing the https://admin.atlassian.com/ site.

If said user has no org admin rights to any organization (or is stumbling on this page for the first time) the user is then redirected to https://admin.atlassian.com/o/create or https://admin.atlassian.com/o/create?from=atlassian-access

This provides the user the ability to create a new organization (see screenshot)

Idea
Either:

• Completely block non-administrative Atlassian Accounts from reaching the https://admin.atlassian.com/o/create endpoint
• Or provide an administrative setting to block the creation of new organizations