Before Facebook, if I lost someone's contact information, and drifted outside of their social circle for a long enough time, chances were I would never ever see or speak to that person again. Before Facebook, if people wanted to organize conversation and cooperation on an information technology platform, the options were to pay $X00-$X000 for a proprietary system, get lucky enough to know about mailing lists, have so…
That said, I disagree with your conclusion. The issues that have come from Facebook and others are due to centralization, commodification of user data, the proliferation of echo chambers and advertising. Universal accessibility isn't the culprit, although that has generated issues on it's own as well.