> people would be better off by switching
In the UK, everybody uses Whatsapp, from friends and family to businesses.
That won't change until communication platforms are forced to make their products interoperable with each other. I can't use anything else because nobody else does, I would not even be able to book my Dog in to the Groomers because they won't answer the phone and only respond to Whatsapp.
E2E encryption can protect contents in transit with TOS for communication platforms to join the Multi-provider network stating they cannot analyse the contents of received messages in-app.