IRC, minus a bunch of technical nonsense nobody who is busy will bother to understand or manage (mode flags, server vs network channels, out-of-band post-hoc client-to-client features, netsplits), with good stories for multi-device (single, consistent cross platform experience) and offline (messages are queued/marked as read server side, in a way consistent across devices) and bots (anyone can add an integration in a few minutes, instead of delegating to a developer to add some code to the latest pet bot which soaks up maintenance effort like a sponge) management (managed, easy access control, no services bolted on as an afterthought) and file sharing (files stored server side, every client and user supports the feature, file can be sent when user's client is offline, doesn't have to figure out how to forward some ports or something) presence (consistent single feature instead of someone maybe implementing away status or an away nickname) identity (nicks === users) and so, so much more.