Your complete chat history with everyone on WhatsApp, to date, has been provided in basically unencrypted form to Apple and Google by your conversation partners, which means that it is available on demand and without a warrant to US federal authorities via FAA Section 702 (commonly known as PRISM, or FISA).

This means that even if you stop using it today, there is a huge wealth of information about your habits, travel, personal identifiers, social graph, location history, and personal thoughts and opinions that will be permanently stored associated with your name.

Enabling e2e on backups won't purge this information, especially if it has already been downloaded by USG from Apple/Google.

If you want to mitigate this, you basically have to move, replace all your friends/contacts, never go back to the same venues/restaurants/cities, et c, because your existing pattern of life is already archived.

Too little, too late.