As mentioned before - this isn't new for porn. The 70s had a lot of it and it was acceptable back then. Just went underground when the 80s - 90s rolled around and everyone was confused. Movies from Hollywood didn't exactly walk away from the topic
IMDb: incest movies - a list by nagendrain
Just some of them - hell even Star Wars had it if you really think about it. Blue Lagoon etc. the list goes on.
In the end - over the years I've found that it wasn't the old guard of the industry that cared but the newcomers who have a sense of entitlement and need to be seen are the ones who speak the loudest.