To be fair, in many cases email addresses are at a minimum 'Light KYC' or let's just more accurately call it personal identifiable information.  Unless you're getting a temporary phone number to verify with, most peoples "private email addresses" are most certainly linked to their identity.

I don't think you understand the concept of nostr login... Your private thing can exist nearly exactly as is, without the need to own the user profiles / account list / social graph of future billionaires using your thing.