Earlier quoted context omitted.
It was Slack/etc years before those existed. They just couldn't figure out how to market it because there were no reference points at the time, so few could see any reason to use it.
I doubt it's just that. If those things were actually great, people would have embraced them like they did slack. Consider Google+ also. They had plenty of reference points for that. It was just not very good. Google tends to abandon development on new projects way too quickly, before they're ready for mass appeal. They probably expect it to explode like Gmail did. But I think they forget they lost a lot of promotors…
"We couldn't figure out how to market it" was from an interview straight from the people who made it: The companies they pitched to responded with things like "why would we need this, we have email".