Maybe it's a tech company thing but we were using irc for years before slack came about. We eventually swapped to hipchat as it was easier for less technical people to join, and later slack when that shutdown.

Almost every open source project I've worked on coordinated on irc back before slack/discord took over so it's hard to says text based communication tools are anything new. What I will give tools like slack is massively improving ease of use for less technical users, which has meant it's now used much more widely outside technical spheres.