I can only convince friends that I have influence with. That means that I'm already in regular communication with them and an active member of the conversation.

Casually bring up some shortcomings about the current messenger and see if others agree.

Then don't jump the gun on new messengers. If it's "good enough", it's usually not ready to invite others. When it is "awesome" is when it's the right time. For example, I only got my friends on Signal after they added user mentions, stickers, and fixed link previews.