IRC is great for public rooms or public meeting points.
I like to imagine IRC servers as virtual co-working spaces. The kind of co-working space with lots of meeting rooms. Each channel is a one of these meeting room, and anyone can walk in at any time. If you were there first in a room, you can ask others to leave or kick them out. If you reserve a room (e.g.: register a channel), you can have the staff kick out unwanted guests. If somebody misbehaves, the moderators or administrator will throw them out of the building entirely.
IRC isn’t end to end encrypted, but it’s encrypted at flight. This is in the same vein that meeting rooms are private, but you trust that the owner hasn’t installed hidden microphones inside the walls. If you need tighter security, you want your own building (e.g.: your own IRC server).
You can also be sure that only people in the room can hear your conversations. If someone walks in, they can’t suddenly know what was spoken before they walked in. If someone is keeping logs, they might leak what you said, just like someone having a recorder in the coat pocket can record anything that happens in the room.
For a public or semi-public meeting point of an open source project, or open community, all this is exactly what’s needed; no more, no less. The protocol is well-established, lightweight and standardised. And there exist plenty of client implementations for a huge variety of devices and platforms.