I'm serious. This may sound incredibly flippant and facetious of me to say this, but that is the solution. The culture here has fostered a community of highly dedicated roleplayers, people who are still around even if they aren't being active. But the fact that they're (we're) still around is what gives us hope of coming back.
The community is searching in desperation for some way to fix this problem, but the solution is right in front of our faces. If you write a good story and take some time out of your day to contribute, the problem literally vanishes because suddenly there is activity. I remember one of the Harrowing RPs where we had MASSIVE commitment and people cranking out posts (and GOOD ones) so fast that some people were asking us to slow down. I copied the entirety of that RP into a Word document for my own records. It's over 100 pages long and it's one of the most intense combat RPs I've ever had the pleasure of being part of.
But good stories aren't going to write themselves. Your contribution isn't going to happen without your effort. That's literally all we're missing.
So I'll say it again. If we as a community take the time and put in the effort, generate some compelling story ideas and then stay active enough to get our posts in day after day, the problem can and will vanish. If you can do one post per day or two per RP that you're involved with, you have the power to make a difference.