Yeah, Facebook is well known for its Orwellian surveillance and political nature. Frankly, I'm shocked at how many folks from this group in particular are OK with that. Still, I didn't know about some of the stuff listed there.
Anyway, it's definitely not for me.
groups.io does seem like the best alternative. We've got several medium-sized (100-200+) Yahoo groups that we'll probably end up converting to groups.io if Yahoo does indeed go away. Those groups are also mostly (either entirely or almost entirely) about email, but having the ability to store some shared files is helpful.
Michael N6MEF