Phone? I didn't mention a phone; both Facebook and Meetup are entirely usable via their websites.

We have about 40-50 active and semi-active members (on Meetup), hold a fundraiser, and yet the organizers still have to chip in to make up the inevitable shortfall.

Whether or not to use Facebook (or Meetup for that matter) is something everybody gets to decide for themselves and preaching about what they should do is silly.

Facebook groups don't require a cellphone. I participate in one (much to my dismay... but that's where the group is...) and I never "Facebook" on my cell phone - messenger, "app," website... none are loaded on my phone or ever used on my phone.