TBH I never saw any real need to use Whatsapp even before the FB takeover; as I get issued a mobile device for work, and even PAYG mobile call and data costs are dirt cheap (or included in bundles) compared to what they used to be, and the harsh reality is global telecoms networks are always going to be accessible to feds/govt/security services, as they are the biggest paying customers of such networks as well as having the power to regulate them.
Giving away your private data to private companies in the hope that they might “make it safer” (without actually paying these companies to do this and then still independently auditing what they are actually doing with it) isn’t going to work.
https://www.theguardian.com/technology/2016/aug/25/whatsapp-backlash-facebook-data-privacy-users