What has disappeared are the "gallery sites" that were easy to make - often by hand - or using basic CMS's like wordpress.
Most of the people who say it is over are the "old skool" industry folks who hate the Tube sites because they represent a level of technical expertise that they cannot match (but most HN'ers can)
What is happening is real technology is disrupting the space and those without skills are getting pushed out.
People are still paying for porn, and content sites need to find the distribution and new leads.
I know this because my partner has a lot of projects in this space. I also know many people - from owners of some of the biggest content houses here in SF thru to engineers who work on startups and supplement their income at night through this kinds of projects.
It's actually more common then you think, most people just don't want to put their names to it.
