I'd just like to add my support to the OP and others who have said that they have noticed an increase in certain sorts of products and proclivities as well as to voice my agreement that, in general, actual showcase quality of products on the site seems to be going down a little bit. But, since I rarely buy stuff and, when I do, it's almost always from someone well-known for product quality, I can't comment on products that appear to be pure crap, but aren't... since I won't buy such products.

I think the solution is pretty obvious:

1. An 18+ toggle on a member's user page that acts as a filter, much like the one used to allow 18+ imagery to be seen by the member. I realize that Renderosity might not want to do that, since it limits advertising exposure and might result in less people seeing 18+ products. HOWEVER, what it would do is allow them to have a broader 18+ product line without offering unnecessary offense to non-members and those who choose not to view such products. (I'd be fine with none of them being offered, since there is, after all, an alternative marketplace for them that has been around for quite awhile, in one incarnation or another. But, I think Renderosity would rather have the sales potential and would be more amenable to using an 18+ filter for products and broadening it's 18+ product-line, as a result.)

2. A better system of quality control and more scrutiny of certain sorts of products. Product-saturation can contribute, remarkably enough, to decreased sales, if overall quality is a question. If there are nine crappy products for every one good product, the entire genre of products is going to be considered crappy, 90% of the time... See how that works? :) So, do we really need three-hundred and fifty-seven hair retextures for one hair model that only demonstrate the creator's skill with a Photoshop Hue tool or filter? No. And, if it makes it to the marketplace, what does that say about the marketplace? What if, instead, it was ten very well done retextures using real reference photos and very good mapping and image editing skills? Yes, we would like those, okthxplz...

Lastly, good taste and appearance matters. It matters a heck of a lot. In fact, one's reputation, whether in business or in any other facet of life, is one of the most influential things regarding one's success that one can control. If one plans to live alone on an island, then that doesn't matter. But, if one intends to live and operate amongst human-beings, it's of paramount importance. Spend it at your own risk...