It sounds like you are suggesting it is not E2EE because keys are backed up to Google/Apple. That’s not true, it still is E2EE. It just by default has a backup of the key.

Sure, if your threat model means you are worried about the key backups and particularly your friends key backups, you shouldn’t use WhatsApp.

I’m not sure how you end up at Telegram with that threat model.. but whatever floats your boat.

I’d wager most people care more about FB not being able to read their messages. And they can’t. Maybe one day that changes but they will be required to communicate those changes.