You’re missing my point, which is that there have been radical cultural shifts in the past 50 years which have completely transformed expectations about sex, re

You’re missing my point, which is that there have been radical cultural shifts in the past 50 years which have completely transformed expectations about sex, relationships, family life, careers, etc. The old pattern might have had less infidelity (though I wouldn’t be surprised if available data about past prevalence of infidelity is inaccurate and unreliable), but it also had many other severe social problems, some of which have improved substantially between 1970 and today. A culture (and the laws, mores, economic relationships, etc. which enforce it) isn’t a simple system that you can poke in a particular way and get a clear and simple result out.