WhatsApp was already great before Facebook bought it. Though they did switch it to the Signal protocol for E2E encryption, which was great. Nowadays, it's still pretty useful. The AI button is annoying. There were some kerfuffles about linking WhatsApp data to Facebook/Insta data, which they promised to (I think the EU) not to do when they acquired WhatsApp, but did it anyway [1].

For the rest of Meta, just read Careless People and the linked submission is not surprising at all.

[1] https://www.irishtimes.com/business/technology/whatsapp-says...