Personally, I think the biggest problem I've seen around here lately, aside from the usual attendance hassle and people-not-reading-the-damn-rules, would be...
Seriously, I've seen people with sign-ups that look weak at best picking on others, whose profiles were unfailingly either equal or better in quality. Similarly, newbs taking it upon them - by some obscure logic which I do not comprehend - to mini-mod other people's RPs, passing judgment like they were some kind of RPing messiahs or at the very least the proud owners of their very own death notes, and - most amusingly - people posting two-liner posts to complain about other peoples' three-line posts and pure OOCs to complain about the OOC spammage. *Rolls eyes* Seriously, guys; common sense and manners. This is supposed to be for fun.
As for the quality gap issue...it seems to be a matter of attitudes, sadly. Most of the RPing veterans are already stretched pretty thin in managing to get their foruming needs done and as such they primarily join RPs hosted by - you guessed it - other veterans because those are the only ones for which they have some kind of guarantee of quality. This, in turn, leads to the spots in said RPs getting filled up by a more or less regular cast of veterans, as their profiles tend to be drastically better than those of newbs. Thus, newbs are either too intimidated or unwilling to put in the effort to join a veteran RP and stick to the ones where you basically get approved for managing to write something - anything - into each one of those little fields in even semi-legible English, in other words: RPs which few veterans would deign to touch even with a ten-foot barge pole, at least for any other purpose than to laugh at and/or be frightened by them. Veterans RP with veterans, and newbs RP with newbs. Newbs don't get to learn from veterans and aren't pushed to writing as well as they really could because the newb RP masters are either completely unconcerned by any measure of writing standard or too scared of alienating RPers to ever enforce it while veterans are stuck playing in their own, slowly shrinking circles because there just aren't that many competent writers to go around. Consequently, we have a huge divide between newbs and veterans that can only really be crossed by those with unusual writing talent, prior writing experience, the right connections or the persistence and will to actually improve on their own. The discussion thread is deceased for all practical purposes and I have yet to find a single RP guide that actually covers IC posting or plot writing to any significant depth, so claiming that there is any real way to self-study your way to being a good RPer with those is questionable to say the least.
At least...that's my take on it. *Shrug*