I've tried this. It's hard to get people to switch platforms when they don't perceive any major existing problems with their current platform.

My neighborhood that I'm on the HOA board for has been entirely on a facebook group. When I joined, I made sure that we communicate all necessary communication via email (for others like me not in the group or on FB). I created a website for the neighborhood that does everything the FB group does and more, but people don't see a reason to visit another website when FB has everything they want, so they still only engage on Facebook.

I'm okay with being the problem (green bubbles are a whole nother thing for friends and family), but without sufficient pressure to switch, people generally prefer what they're comfy with.