Then delete that data and let the user start over. How come Apple gets to hold iTunes purchases (apps, movies etc.) and somebody's email address hostage just because they also happen to store some end-to-end encrypted data on the same cloud account?

Just imagine Google letting people "brick" their accounts because they have a password protected PDF in their Google Drive they don't remember the password for...

And that's to say nothing about the not end-to-end encrypted data, which is still the default for most things in iCloud accounts (without ADP enabled).