I wonder if the proliferation of easily accessible porn on the internet may also be a factor. People literally have access to porn 24/7 in their pocket if they have a phone.

I don't think porn fulfills the same niche. Movies have room for greater story telling, character development, and a realism that the viewer can connect with or feel emotions from. My armchair take is that the erasure of sexuality is most tied to the fear of appealing to modern audiences who are easily outraged at anything that offends them. And so the movies all tend towards a boring beige, a formulaic re-skinning of the movies that came before them. The MCU is a great example of this.