Not the same posters, but yes, that is what it is esentially. People are starting to notice that they don't actually want "social networks". Most people are not interested in constantly curating an optimal public image of themselves. What people want is communicating with people they like and share interests with. Slack and Discord are basically efforts to make more user friendly IRC. There is nothing wrong with that. (Except of issues with centralization and non-standards based communication)