Maybe you should go back and read scoopdewoop's comment again. Half of their point was that slack and discord are not simple text only chat clients.
Try using the global search feature on Slack and tell me how that already existed in IRC circa 1995.
Isn't that particular feature mostly implemented server side?
On the other hand, yes, I agree that modern messengers has a lot of features that my IRC clients missed (voice comes to mind). Also they are easier for mainstream users to use and administer, and, compared to old IRC, safer in a number of ways (although I'd add that we are seeing a number of new threats now).