I highly doubt that slack has more features than IRC, which has thirty years of history in dozens of code bases. I agree that taking a canned solution is easier

I highly doubt that slack has more features than IRC, which has thirty years of history in dozens of code bases. I agree that taking a canned solution is easier, and easier is often best. But I think this is the main reason slack is popular; its less to think about. There are many dimensions in which it will be worse.