I'm not sure why everyone is downvoting this. To repeat myself from another thread: give people generous readings. Slack isn't literally a modern accessible IRC client, no, but it's "today's version," i.e., today's equivalent. Slack is absolutely IRC-inspired, and services like IRCCloud[1] suggest that it'd be possible to build most of what Slack "adds" to IRC on top of IRC's existing protocols.
In a lot of ways, I think Slack's biggest advantage has just been ease of use in modern times: you don't need to know anything about downloading a client and configuring it -- even the friendliest IRC clients I've found are still pretty fiddly compared to "enter your team name, your email address, and your password, boom, done." But this seems like it'd be a relatively easy problem to solve.
[1]: https://www.irccloud.com
In a lot of ways, I think Slack's biggest advantage has just been ease of use in modern times: you don't need to know anything about downloading a client and configuring it -- even the friendliest IRC clients I've found are still pretty fiddly compared to "enter your team name, your email address, and your password, boom, done." But this seems like it'd be a relatively easy problem to solve.