Not sure about others but I have successfully been able move many people over to signal from WhatsApp and fb messenger. And many friends have done the same too.
WhatsApp is still pretty big in India though.
Bought that something from someone a few years back and gave your phone number to them? Thanks. Now their hot deals messages reside right next to the messages from your family and friends.
I'm expecting good amount of market share loss once a good alternative is found that focuses purely on personal or group messaging and not on business spam.