By decline do you mean some of the old school community sites being less active these days? Many of those sites preceded my involvement with RN, so I don't have any insider info there...
In terms of marketing your site, you have to be patient with that. Our target audience at this time is relatively small. A large part of the reason I did this site the way I did, was to promote RN; and what could potentially be done with it. "Web CMS" is actually a popular CMS related search which is the reason my domain is worded that way (and that it was available to register; it wasn't my first choice).
With RavenNuke in general, as with many things on the web these days; there are so many CMS platforms available it can be hard for RN to distinguish itself from the crowd. Considerable thought and planning has been put into our next release; with this in mind... So hopefully over time our user base will increase as we find our niche in the marketplace. Although I don't have an objective opinion, it's perfect for me. I might compare it to a classic car, it may not have all the latest bells and whistles, but you don't have to be an expert to open the hood and do a little work; and there's something that just feels right driving it
On a depressing note, Google doesn't seem to give out much search engine love until your site is up for a year or more.. Not sure my opinion of Google Plus yet, but creating a Google Plus page might help, as any posts you make there make their way into search results in a matter of minutes. Out of any of the social services I probably prefer Twitter for it ease of use, although they are looking to "monetize" it (more ads) so not sure what is ahead. Some have started using app.net but at $50yr to join, or $100 if you want api access, I don't see that ever going Twitter big.
So for now I think your doing the right things... Create a Google sitemap if you have not done so already (nukeSEO Sitemap) and tryout google+ and twitter, I'll make sure to follow