If people want to get in touch with you, they'll do so. If people want to broadcast information only to those following them on one service, then you'll stop getting that information. That's fine. Other information will take its place.
A lot of us use FB for organizing, not just for seeing what our friends ate for dessert last night. It's not reasonable to tell people abandon one channel without suggesting a replacement. You might as well ask people to give up email, or their phone.
I'm sorry, but this is ridiculous. We're talking about a company that has knowingly promoted white supremacists groups for the sake of clicks. I think that warrants putting just a little effort into email.
No tool is going to do your job for you. If Facebook succeeded where email failed, it's just because someone wasn't doing their job, not because of some special sauce that Facebook has.
You'd be surprised how crap email is for any of that. You'd be surprised how people don't want to have 10 different apps for all the activities and prefer one central source to catch up on everything. Facebook can be very useful.