Depends on how old you are and where you live. As a college student in North America, everyone uses Messenger, nothing else. How would leaving Messenger work without shrinking your social circle to 0? In other countries, like where my family lives for example, no one uses Messenger or has heard of it — everyone is on Whatsapp. So depends on your demographics.
I just sent out a message to my family's WhatsApp group and my jobs WhatsApp group that I'm moving to Telegram because of the shit with Facebook. Adding to that, that they can always call / text me.
My family has entirely moved over to Telegram, though I think they also still use WhatsApp. It doesn't bother me - change starts with yourself.