But the thing is, once a community reaches a mid-to-large size, certain kinds of people will always going to think it's full of jerks and trolls, and that its golden age has long passed--regardless of the community's age or actual composition.
I run one of the largest online writing communities online, Scribophile. We've been around going on 9 years and I personally pride myself on the reputation we've earned as being a friendly and supportive community. By and large people seem to agree. And yet every now and then we still get people complaining that Scrib members are out to get them, that everyone is mean, that Scrib's golden age has passed. (I started hearing that same golden age comment about 6 months in, by the way).
I think the truth is more like the faceless, voiceless, anonymous internet makes it really easy for people to both a) be jerks, and b) misinterpret harmless posts as people being jerks. I think this phenomenon happens in every mid-to-large sized community, ever. And I don't think it's really helpful to criticize any community of that size as having nothing but mean people, or trending towards meanness.