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.
I think the expectations of e2ee have been greatly stretched in this case. e2ee means that the data is encrypted from device to device only and that's it, from one end to another end. If someone backs up their device in an unencrypted way then thats out of scope for WhatsApp - that's not what e2ee is about.
People that expected full at rest encryption (which is what a backup system would include) despite the app never being advertised that way would have always needed a large kick to realise that isn't the case. Encryption is complicated and you can't expect everybody to fully understand what e2ee/at rest/etc really means. This whole situation is a learning experience for everyone and I wouldn't blame WhatsApp for it either. They now know that advertising encryption needs a little more explanation.
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.