I stayed away from Facebook for a very long time, but have been using on-line motorcycle forums since 2003.
I only started using Facebook when I started up my Helicopter business, as that was the best way to get to new customers/students and to keep in touch with what was gong on in the local user groups and training schools. Once I got into it, I realised there were other benefits, as well as trade offs, so I've stayed a constant user, although a pretty infrequent poster.
Prior to my business use, the only experience I had of Facebook was from 2010 when my son left his very new, very expensive iPod, on the plane we took from Heathrow to Denver. He was devastated to lose it as it was a gift from a very dear departed relative and the first few days of our holiday were miserable as a result. But then, he saw message on Facebook from someone who had found the iPod in the seat pocket on the plane and contacted everyone with his name on FB - they said that if anyone could send them the inscription engraved on the back of the iPod, they would return it. By the time we got back home, the iPod was there waiting for us. The finder refused any offer of payment for the postage or their trouble (they were from San Francisco) and once our son knew his iPod was going to be returned, our holiday became the happy event it was supposed to be (the iPod had sentimental music put on it by the relative to remind our son of their time together and friendship).
Both my hiking friends and my cycling friends use Facebook groups to share info, rides/hikes, training updates, social events, photo's, route maps etc and so do most other friends. My other uses of FB include Motorcycle Groups (for all the positive reasons noted earlier in this thread) and our local Community Groups.
The Community Groups are fantastic for keeping everyone informed of what is going on, local news, local meetings, local events, lost and found pets etc, but most importantly it's a source for seeking help - I've become known as a bit of a local "handyman" by helping a large number of residents/neighbours, since I retired, doing everything from disposing of old garden sheds, fixing taps and toilets, laying paving flags, getting cars going, rescuing stuck kites, loaning out my trailer, building things such as sheds, planter boxes and timber stores, as well as lending out tools and clearing gutters (I have a set of ladders that can reach the roof of a 3 storey dwelling) ................... but most especially during this recent pandemic and our lockdowns, it has been vital to help our Covid Support Group to keep in touch with isolated, vulnerable residents, who are unable to do their own shopping, dog walking, or to get to medical appointments.

Facebook is vital in today's world for Volunteering and Charitable Groups, not only to seek funding/support, but also to get their service in use and helping people.
As far as I am concerned, the benefits far outweigh the negatives - especially in our local community.
As Noel's hacker said - its all about how you use it and how you manage your settings. I don't get bombarded with unsolicited adverts (except those really useful friend requests on Messenger from single and married women, local to me, offering various "services" for free if I click on the links to their nude photos

) and I use the ignore function to avoid seeing stuff from people/Groups I don't want to see.
BUT, I do get to see a lot of politically motivated stuff from people that, if I was politically minded could upset me, but at the end of the day, everyone is entitled to express their own opinion, whether I agree with it, or whether they're wrong

however, to be fair I also do enjoy reading other people's opinions, again even if they're wrong.
I won't be leaving FB or Social Media in a hurry, but I understand and respect the choice of those who do - it's your life to live.....just enjoy it
