Most of it is written by hormonal schoolgirls - that's the bulk of the fanfiction and amateur adult writing communities in a nutshell.
If you'll permit me to engage is a little bit of largely unjustified gender stereotyping; women tend not to succeed writing erotica for their own gender because they write stuff that appeals to them personally. Penning erotica is about hitting as many of the different bases is quick succession as you can; every reader has very different tastes and you've got to appeal to as broad an audience as possible. To do it well you've usually got to be a completely detached cynic. As soon as you get invested in what you're writing it quickly becomes unappealing to the majority of your audience.
That's why I found it so fucking boring. I've written about fucking, and I've written about camping. The camping articles were more enjoyable.