Such behavioral, preference, lifestyle, openness, and attitude changes include: Alternative gender/sexual identity expressions diverging from family focus, stress/anxiety, voluntary celibacy, perfectionist family planning (contraception, abortion, workaholism, and stricter goals), shallower human interactions, disillusionment of love, casualness of increased divorces, elongated adolescence, extended non-monogamy, "failure to launch," distractions like screens and video games, and, inadvertently, fertility reduction causes like obesity and plastics. I'm certain there are more factors I missed and some that are minor.
In such an environment, wouldn't evolutionary forces be less likely than, say, ubiquitous xenoesteogen exposure from new chemicals like plastics or a vastly different diet and lifestyle from our evolutionary origins?
People with scarcer resources have more kids.
It’s certainly bigger than any one human directed agent.
But yeah we can’t prove it.
I think we can only look at history, macro trends, and some imprecise civilizational differences to throw approximate qualitative hypotheses against the wall to make some guesstimates, and still be wrong most of the time due to unaccounted factors or even happenstance of maladaptive random behaviors like not dating people with green eyes, political revolutions that organize society differently, or inexperience/shyness denying the immense rewards of social/sexual/pairbonding opportunities.