I hope Threema is gonna be able to interoperate with WhatsApp as I’d love to ditch that app.
Just a setting preventing new people from your contacts to write to you on WhatsApp would be great. I only keep it because of some groups I can’t leave..
It's not the technical side. They are scared of metadata leaking and making their network less secure. If you want a dezentrale messaging to work take a look at matrix.