Nor am I, but it’s possible to customise oneself a stripped-down Facebook account specifically for participating in Facebook Groups. A nickname, if you wish; no personal information; no ‘wall’ of person posts; no Messaging; no ‘Friends’. And (using add-on F.B.Purity), a plain, uncluttered page with NO ADVERTS.
I share all manner of very serious reservations about Facebook, personally, commercially and politically.
So it’s well worth saying that Facebook Groups is a world away from ‘ordinary’ Facebook. That may sound strange given that it has the same ‘look and feel’, but it operates very differently indeed, through specific Membership rather than a vast intertwined Network of ‘Friends”, “Friends of Friends’. Yes, it’s still Swimming with Sharks, but better caged.
Yahoo Groups is presently unsupported, is doing weird stuff, and is yet to gain the attention of its new owners, for good or ill.
If Yahoo goes under, our present Best Shot at an email group is 'Groups io’, designed and supported by the geezer who originated what became Yahoo Groups.
Admin for many Yahoo Groups which I still much prefer.