Hmm once you teach someone to use WhatsApp, another messaging app shouldn't be that hard to learn. I believe FB have been very careful to prevent misusing WhatsApp platform (or have been very good at keeping the misuse secret lol); if word got out that they were it would certainly lead to a huge exodus.
The problem is what they've learned is mostly to do with what icons (which they have no context for, never having used a computer or smartphone prior to this) they press to get certain results. And we teach them this over an audio call, so trying to learn a new one would definitely be a challenge.
But overall I would swap back to different apps were WhatsApp to be 'compromised' or misused. Discord text chat for my gaming group, Signal for some tech chats, etc.
Overall it's a shame, since I was very appreciative of the approach the Whats-App founders took. But if we're lucky, WhatsApp will remain mostly the same for a while.