You know, an odd example is Patrice Chéreau’s movie Intimacy.
It is very explicit, somewhat on par with amateur porn. In fact, at least one scene “features” an unsimulated sex act, and it’s possible there were other scenes which included penetration, although it’s not certain (about the latter).
But the “love-making” itself is drab, and sad. Merely a mingling of exposed bodies. I didn’t find it erotic in the least. Which I think is the point of the movie, really: how does one achieve intimacy among characters who are disabused of the notion?