If there is a key which decrypts everything, then there is a risk it can be stolen or guessed and used to decrypt anyone's messages. This risk does not exist in current, properly designed systems.

Any government which wishes to add a backdoor to an E2E encrypted messaging system must understand that they will be HEAVILY undermining the security and privacy rights for all users of the service which has the backdoor.

Whatsapp decided to go for E2E encryption for commercial and marketing purposes following all those privacy scandals.

They did not have to. They could have gone with P2P encryption, i.e. that their databases could have stored messages in cleartext. That way authorities would not have needed to ask for any backdoor. As already mentioned, this is how cellular operators work (that's obviously something governments wanted).

I think we might see legislation brought in in the future in order to force this.

Okay. Let's just get rid of E2E entirely and let Facebook mine not only our metadata but also the content of our messages. Nice plan.

> let Facebook mine not only our metadata...

Don't use Facebook, then.