I'm thinking a huge part of the difference between Slack and IRC audiences has to do with the $340MM Slack has raised. If someone gave "IRC" a quarter of a billion dollars, the differences might not be so obvious.
that's just the nature of the beast, x.509 is also very old- but old things should be fixed or replaced with better alternatives, slack just fixes a usability problem.. but trades all privacy and freedom for that.
Personally it's not enough, but google has a massive market share because normal people do not consider that their data or freedom has any worth.
at least google is pro-free market in the way that you can extract data out later and migrate, I don't see slack being able to offer that reasonably. (or their incentive to allow it)
2. Using cloud services in exchange for contributing to aggregate data seems like a pretty clear understanding of personal value.
The stuff IrcCloud, Slack and HipChat undo? That's the stuff that seems to be alluring to the steadfast IRC users. Inscrutable commands, nick and chanserv and unencrypted passwords sent via a command that could very easily be typo'd to broadcast in a channel, obscure partitioning behavior that is very much not what most businesses want, a lack of accountability or verifiability, a lack of robust logging and search...
I say these in a negative way, because that's my perspective. For many people they'd list many of these in positive ways like, "improved anonymity", "off the record by default", "network robustness", etc.