I can't speak for the community, since I don't engage in it, but the Bad art is mostly just a consequence of
Sturgeon's Revelation. Deviantart is the most popular western art website (Though I imagine Tumblr is going to supersede it in the coming years), so it only follows that most of the art would be middling or worse, since so many people are contributing pieces. That, combined with the
Theorem of Narrow Interests means that finding a high quantity of low-quality art is inevitable, especially so for niche fandoms or unpopular characters. As somebody who spends days at a time browsing for art on Pixiv, there's a
lot of chaff to sort out even on the best of public creative websites.