The idea that WhatsApp data is shared with Facebook and the rest of its services is something that users did not like. It caused many to migrate to other apps and Telegram together with Signal were the great beneficiaries. Finally WhatsApp decided to postpone the entry into force of the new conditions.
For Facebook, the big problem with this update is that users have not been able to clearly know what the real change is taking place. The not clearly convey that information remains private conversations is what has caused many users choose to go to other platforms. Other platforms that are often even less secure than WhatsApp by not having end-to-end encryption, as is the case for example with Telegram.