Right, but this is kind of the point. Because Slack is more approachable for the masses, it wins in these scenarios. It doesn't need to convince the longtime IR

Right, but this is kind of the point. Because Slack is more approachable for the masses, it wins in these scenarios. It doesn't need to convince the longtime IRC users to move across, just the ones that see barrier to entry on IRC as enough of an issue to make the switch. Exactly what happened in Wordpress' situation, it seems.