If we are including all fetishes and kinks, then any photo, video or drawing that shows feet is porn. The internet has a massive foot fetish. Some people are aroused by eyes. So any photo, video or drawing that contains eyes is porn. Some people are into ... I mean, I could keep going but it's already silly.

There used to be clear lines drawn for porn penetration, oral copulation, etc... but those lines have been quite burred. Now anything lewd could be porn and just about anything could be lewd in the eyes of the beholder. There's some case law that tries to put bullet-point requirements on this but is still somewhat subjective even when stare decisis is utilized.

Overall I agree with you. The government should stay out of it. The tech industry should also stay out of it. Just add a header for URL's that may contain user-generated content and let the clients decide what actions to take or not take on that header.