Sex is not harmless. While it is one of the great human joys, it is also the source of some of our deepest despairs, intractable conflicts, and personal tragedies. This free-for-all free love ethic that you celebrate, which erased almost all of the previous social restrictions on sex, inevitably created the discontent that boiled over into the #metoo phenomenon. It is also fueling the growing incel phenomenon.
It is not just out of backward thinking that every single human society has seen it fit to strictly control sex. The last half century, where your attitude largely reigned in Western Europe and almost the same extent in America, is an extreme aberration and it is ending rapidly before our eyes.