whatsapp's killer feature was "no killer features, just a messaging app with number-bound IDs and good UI that even my grandma can use with minimal setup". for anything like that again I'd change, but the minute they think they need to add something like numberless IDs, or stickers, or a social media feature, or a payment system, they can fuck right off.
WhatsApp killer feature was "No paying for SMS ever, just your data bills", which was much lower than SMS fees in many many countries, which also explains the popularity of WhatsApp outside of the USA and in many Asian countries.
And it was tied to your phone number instead of a login ID, so anyone with a WhatsApp sign up could interact anyone else who had it, instead of having to find your contacts again like with a new IM service.
It's not a killer feature that they need, they need user base. There's no reason for people to leave WhatsApp, as long as people can use it.
Here in Brazil, the only surges in Telegram popularity and actual usage where when WhatsApp was blocked countrywide, and even then we had several people downloading the shadiest VPNs out there just to log in on WhatsApp