I tend to agree. But there is another aspect: Sadly the democratization of internet access has lowered the bar across the board in regards to both form and content of discussions in communities.

I've been a heavy forum user and occasional mod/admin in subject focused communities in the pre-Facebook era (~'98-2005) and I've seen many communities die down from an influx of barely literate (technical or otherwise), low effort, entitled and sometimes rude users. And I don't think this can entirely be explained by the "mainstream otters" concept, and neither have I seen many instances of new niche communities appearing to replace the former. At the risk of sounding like an elitist, I observe that the education level of the average internet user has been dropping.