That said, and as the author touches on, the action/super hero of today is a PG-13 one. Studios need to reach the widest audience possible to make the most money, so it's a safer bet.
Sure, back in the day studios had the same imperative, but the licensed toy game was still young, so they didn't realise that maybe if they made Die Hard PG instead of R they could sell some John McClane action figures to younger viewiers.
Nowadays, that's basically the starting point; what we can we sell outside of the movie? how can we milk the franchise for as much as possible?
And that's where a lot of the sex appeal is lost. Marvel movies can't be as raunchy as a result.
Another topic that the author touched on was the way the ideal aesthetic has changed in not just our bodies but where we live or what we do in our spare time.
I agree that more and more we are optimising for artifice; fitness classes, extra curricular activities, holidays, concerts and events we attend, just to keep up an appearance online or in person. And in those activities we often don't get the true value out of them because we're doing them for the wrong reason.
Anyway, it's a complex and interesting topic and I'd love to read more about this perhaps from even further back (50s or 60s) if anyone has something similar to this post?