> but it's easily doable for everyone on this site
And that's where you lost sight of the big picture. Slack is _not_ for people on this site it's specifically for people out there: people who don't know and don't need to know what a protocol is, who don't care about netsplits, who couldn't be bothered to install some random stupid stuff on their machine and spend an afternoon configuring it just to be able to talk to their co-worker. We're not the target here. And yet it has convinced some of us because it ticks so many boxes by default.
Quassel on the other hand is to Slack what Seafile or NextCloud are to Dropbox — definitely not as comfortable, as you need some knowledge to self host it, but it's easily doable for everyone on this site, and once it's set up, it's just as comfortable.
Of course, if one wants to use a hosted service, there are solutions like that — IRCCloud is pretty much identical to Slack, except based on IRC, and in addition to paid team workspaces, you can also connect to any IRC network and use the same features there.
So, you see, while it has some hints of the same attitude as the original post — and definitely, neither of these products is as polished as Slack, after all we can't make 380k$ losses a day, while Slack can — they fulfil pretty much the same purpose with pretty much the same ease of use
And of course work on single-click deployments and hosted services for more such products has already started