Well, I've not been on this site long enough to comment on the "good ol' days", but from an outsider's perspective things seem pretty lively. On forums I've frequented in the past, even though I confined myself to the Advanced section, I knew everyone, including people who only stayed in Casual/Free. There were new threads and IC's daily, but only a handful that had any longevity. Now if I compare that to the Guild, where I constantly meet new and new RP'ers and see tens of threads pop up over the various sections (well...apart from NRP, but then again that's always the case with NRP), can't say I'm noticing a downward trend. So I'd say things are just...different, not necessarily worse.
In terms of what types of RP's get posted, well there's always stuff that's more popular than others. Based on my observations during the past decade, I'd say it's cyclic, like most trends & fashion. Besides, if you didn't have derivative RP's, how would the truly good ones stand out? ;)