Irc frequently has a very low active to inactive user ratio. Part of the reason for this is people just stay connected all day but only occasionally check on any particular channel, and even less often participate in a discussion.
As for #cataclysmdda, I don't know if there are any active devs on there nowadays. I used to be on there pretty much nightly, but I'm rarely on now because I'm either taking care of baby granade, furiously merging changes or furiously bugfixing. Gone are the leisurely 4-hour coding fests every evening punctuated by irc chats every 30min or so ;_;
In general the pace of irc takes some getting used to.