Honestly I think "the beast" is so large that it defies simple expectations like that. The readers are as varied as the authors. There definitely are readers who are craving that longer form, higher quality story, some get in touch. But there is also positive feedback on the simpler, shorter, more titillating stories. I think both have value, at different times, to different people. All that really tells me though is to not write to appease the audience, but to write for yourself instead. I'm sure I said as much to Tigerstretch in the earlier days - audiences are fickle, and often unappreciative. If you're not writing things that you personally want to see out there in the world, there's no point.
I wouldn't read too much into the fact that the Plaza survived. I think that it very nearly didn't. Different historical decisions, personalities, personal circumstances, all could have made the difference between it still being here, and the number of stories posted dwindling to nothing and then eventually the site just goes offline due to neglect. I'm fairly sure that stubbornness, Gromet's and mine, plays its part.
It's very much a feedback loop, from what I've seen. The sorts of stories posted affect the sorts of readers that keep returning, and the sorts of authors that choose to submit work. That cuts both ways - positive and negative. I've had first hand accounts of that from readers I've met in other places, being candid with me about how the sorts of content posted affected their perception of the site, and in turn reduced their desire to submit their own work. It is why I've started to be much firmer about passing on the low quality submissions, and the darker, non-consensual material. Because the site can't be everything to everyone without being mediocre or bad to everyone too. So I'd like it to be a place where good, thoughtful kinky stories can live alongside playful, light, sexy tales.
I can't speak for everyone though, obviously. I'd love to hear from the other longer term readers what they most enjoy. There's no wrong answer, naturally, different sorts of things appeal to different folks!