I can't speak for others, but let me tell you how I've used it:
-to go through badfics I already know I won't mission, but would like to share and boggle and rant at and analyze with other people joining in all of that. It's fun, it's interesting, it's writing critique--it's a slightly intellectual form of entertainment.
-to go through bits of badfics I am missioning, because I want to share a bit of it (without talking too much about the mission itself) and am a slow mission writer anyway. It also sometimes leads to new ideas for the mission itself, or the outcome--for instance, in one case I worked out that I was definitely rescuing a particular baby and another Boarder helped me name him.
-as a form of advertising. Much like a more in depth version of a badfic thread on the Board, going through a badfic in the channel brings it more thoroughly to others' attention, and sometimes (relatively often, tbh) results in someone deciding to claim it, or to claim it pending Permission. It doesn't happen with every fic, just as not every fic posted here gets claimed, but I've seen it happen a good few times.
So. While I'm still in favor of a bit more transferral of cool/interesting things from the Discord over to the Board (in the sense of making posts about it, not moving over--there was discussion of this a while back, some of it from me, though I'm not completely sure which keywords to search yet and can't do it right now anyway), I don't think it's bad that the Discord exists or that it should be limited or something. Encouragement to make more Board posts and to share more of the fun things from the Discord (remember, there are Boarders who aren't on there, or who only pop in once in a long while!) is one thing; however, I don't think it's taking anything away, really. There's been a form of chat lounge for a very long time; moreover, the idea that it's draining away the PPCness of the community...
Listen: I've been here since early 2013. Longer than some, not as long as others, yes, it's a bit of a yikes moment to see that mean it's been a while...I'm getting off track. My point is: when I became a Boarder, the Board was not purely a place for writing discussions! There were bits of current events, science posts, movies coming out, life event announcements that weren't all writing related, Gathering reports, silly posts about quizzes, silly posts about pretty much everything...
There were also, of course, all sorts of writing-related posts: writing questions, PPC-related questions, RP posts, writing challenges, the occasional writing workshop from PoorCynic, movie reviews, hypothetical questions, questions connected to fanfic writing, questions/threads about writing philosophy, PPC-specific threads like story announcements, beta requests, Permission requests, wiki questions, the various annual events (shipfest, badfic games, eventually Plort, a handful of others that are a little less annual), etc...
As far as I can tell, we still have a lot of that going. It's ebbed and flowed throughout the years--heck, I'm not just talking about 2013 here to begin with--but whenever something vanishes, at some point it's often brought up again as 'hey, we used to have this going and it was fun, how about we do it again?' and it gets restarted. Sure, we should absolutely get excited about the new Board and hopefully see it as a reason to post more, and, as mentioned, I'd be supportive of more posts about things from the Discord, but I don't think the essence of the community is anywhere near draining away. If anything, we've just been able to move some of what might once have been smaller random chatting/supportive discussions into somewhere with a larger audience! (Disclaimer: I was not in the IRC at its heyday, and, in fact, only went in once or twice and found almost no one there. It's very likely that it functioned pretty similarly; I wouldn't know. What I do know is that I see on the Discord similar sorts of discussions, whether serious or just chatting about shared interests or silly things, to ones I had in private or small group chats in earlier years. Mind you, if that is how the IRC functioned...congratulations! The Discord has worked out well as its successor!)
There's probably a lot more writing going on behind the scenes than is apparent. A lot of us are in some form of school; those who aren't have often entered the working world. Writing, editing, revising--it takes time. I have stories I've been working on for years, and I know I'm not the only one. Heck, even recent stories that have been written and finished within months--you haven't seen them yet because they're still in first draft or betaing stages! Believe me, there's a lot of slow writing or slow editing happening that isn't talked about constantly because one doesn't really want to give constant updates on how slowly something is happening (or to get people excited over and over about something that likely won't be done for quite a while yet).
Another writing behind the scenes point which is more personal but, who knows, potentially relatable to others: we change, develop, as we grow. For me, one thing I suddenly realized had changed was my writing style. It made it very hard to want to continue older stories, both PPC and not; it also, for a time, made it rather difficult to think up new ideas and have faith that they could go the distance. I'm not sure how much of a drop that caused in my PPC writing, though I do think that point coincides with a time when I kept starting, stopping, and completely redoing a small set of PPC ideas, so...yeah, I'm pretty sure it had an effect. I don't know if others here have experienced something like that, but given a lot of our non-teenage contingent seems to have joined as teens and now grown into mid-twenties or -thirties...well, it seems possible, anyway? Anyone's welcome to weigh in, should they wish to.
(Also, yeah, we've never really...done the advertising thing. That's okay. See...I can't check from this page, but Cassie, Neshomeh, or both have already said what bears saying on this topic, I think, so see their posts.)
It could be nice to have a compilation of recent missions, but...we have that. It's on the wiki! We could direct people there, along with TOS, but otherwise...well, it's right there on the sidebar of the front page :)
And finally: regarding AO3...yeah, I probably have more interludes to put up there. We'll see when I get there (and hm, a good number are co-written, so that's a brief discussion...). More important, I think, or at least equally so, is continuing to add publication and setting dates to story docs! And I need to rewrite Dawn's wiki page, though at least the story list is pretty much up to date...
Basically: many little projects. Many little RL projects, too. I'll get to them all eventually.
Anyway, those are my two (more like five) cents.
PS: Breathe, Neo, though presumably you have by now. It's good that you made the post--it's sweet that you're concerned, and a bit of good reflection/discussion/context about the Board's past seems to be coming out--but while there are probably some small changes that would be good to make, panicking is, fortunately, unnecessary.
PPS: A little anecdote regarding the vitality of the PPC:
When I found the Board in 2013, I'd already been reading PPC stories for years. I'd found them something like 6-7 years earlier, around the point I really got into reading and writing fanfiction, and had read...pretty much whatever was available around that point, as well as related stories like OFUM and Suedom. By 2013, I hadn't read them as recently, but still remembered them and the setting...and I was writing a Mary-Sue parody fic, and decided I'd like to swing by and try to find a surviving member or three (about all I thought would still be active) to ask for permission (yes, lowercase) to write in a couple of agents for an outtake.
I didn't find three people.
(I found roughly a hundred, and a pretty active community. I wound up joining because someone asked if I was planning to go for Permission, and I wasn't, but then I started thinking about it, and that was it, I had plotbunnies coming out my ears and started developing agents. Three months later, I was still skipping around excitedly because oldbies were talking to me a bit and then that became excited jumping because aaah, after probably a month or so of carefully editing my Permission request, I'd submitted it and was successful. And the rest is that it kind of took over my writing life, to a certain extent, etc, etc, my point is...right, that the PPC Board is a lot better at survival than one might expect. Even when it has to move!
Also, returnbies. People do come in and out a lot. It can take months or years, but people often pop up again if they didn't intend to leave forever.)