Key to remember that in the Golden Age of Porn, probably less than 5% of teens had seen a pornographic film. Today it's probably over 99%?
If anything we just don’t see what people do in their private lives that much. Incel isn’t some new thing, it’s simply more talked about today.
Also, it's worth considering that the "porn" they would have had easiest access to was Playboy magazine content--not the catalog of Pornhub.