Without delving into too many details, those presumed benefits of Signal matter very little in practice:

• Signal, just like WhatsApp, is centralized: as brokers of your messages, they do know your social graph. In the case of Signal, they “pinky swear” not to look at it, but that’s not a technically enforceable guarantee (impossible by design). The same applies to metadata: Signal can absolutely infer from your usage patterns (frequency, time, volume, …) the nature of your social graph, or if you are rather at work or at home, in a romance or not. Signal can absolutely tell where you are based on your IP, or the device you are using. Worse, while they swear not look, not to care and not to log any of that, just by relying on third-party services and running in the cloud, they expose all this metadata to less trustworthy parties who will do the caring and logging as they are mandated by law.

• Nothing that can be said (or even proven) today about Signal is evidence that the same will remain true in the future. Signal can figure that it costs a lot to operate and might seek other financing schemes. Or its developers can be compelled by law enforcement to alter the service without public disclosure. It all boils down to “nothing is eternal” and while we can’t tell when the demise of Signal will occur, history proves it’s inevitable, and on this path it might turn as unlikeable as you find WhatsApp to be today.

The only way forward I see is to break away from the centralized model: by design, it can’t guarantee your privacy ; by operating principle, it can’t guarantee its sustainability.