Edit: This is not meant to be a complete list, just one example of something incredibly valuable which eclipses online communities. IMO obviously.
Though for humanity as a whole, obviously access to information is the biggest deal. But why stop at education? People today have more awareness than ever about everything. In some cases, including things that average civilians would never have gotten to see, like government leaks, or videos of executions.
And neither of those things are always positive obviously. Not all educational materials are good, not all communities have a positive effect, and sometimes there's just too much information to find the signal in the noise.
So I think it's fair to argue either really. And, truth be told, it's possible we couldn't have had one without the other, given how much individual people have contributed to the internet knowledge stores.
I wonder how this worked in the past. Were people less "weird" that the people they knew IRL were enough?
Today, people seem to only want to hang out with people who are like themselves, who completely accept them. If someone has a different opinion or a different interest, they’re a predator trying to eat your herd.
With a computer & internet access, it's easier to stay isolated. Though I guess TV and radio, even newspapers and writing for pen pals also provides the same substitute sort of-interaction without actually having to interact.
For all the negatives (assuming we say 'all these people should just go out and socialize' - unfairly), I think online communities make a huge difference to those who are physically disabled, need to stay home to care for someone all the time, or are stuck in the arse end of nowhere.
There's still a certain sense of egalitarianism in internet forums. One commenter's opinion is (by default) worth the same as another's.
That said, in most open comment sections in modern times the actual 'community' part is underdeveloped. Everyone is so loud, there's always someone positively thrilled to play devil's advocate with maximal cynicism, always someone there to interpret a comment unfairly, precious little sympathy for the views of others.