Functionally, this is nearly the same as slack, but it's missing the aggressive venture capital funding and marketing team...
In what way is its functionality "nearly the same as Slack"? Or are people these days just using Slack as a generic term for "channel-based chat" without acknowledging the long history of chat apps? (In which case I would argue it is much closer to the functionality of IRC, if still significantly short of it).
With that said, I seldom used IRC so this is a genuine question for people who used it and miss some features.