I can tell anyone in any kind of role (senior to junior, technical to non-technical) on my team to "Download (the/a) client for X and join #channel #channel2" "Follow the directions to set it up so changes on this Trello board are posted to #channel" and reasonably expect they will succeed if X is Slack, but not if X is IRC.
1. Download IRC client.
2. Pick a nickname.
3. Pick a server.
4. Join a channel.
Yeah, here's where you fucked up reading my post.
> anyone in any kind of role (senior to junior, technical to non-technical)
I'm talking about Joe Frontend, Billy Design Intern, Gary Office Assistant. Maybe you work on teams that are 100% neckbeards that aren't afraid to crack open an RFC to get daily shit done (and waste huge amounts of company resources on things that should be simple), but that's not the environment I'm talking about.
Not accounting for these people is the fatal mistake made by far too much of the tools and processes in software. I've watched people go into shops like this as non-technical helpers, work really hard and skillfully within the boundaries of their role, but get burned too many times by a hoity-toity technical bro "lol, you can't even open an ssh tunnel to the bastion host to connect to the internal IRC..." that they quit software, return to lower paid job they did during school and decide they have no skills, when they would thrive on a more balanced (and more socially skilled) team.
If there were no other alternatives we could probably manage somehow, but there's much less friction in "here's the URL, sign up with your email address"