I wonder whether it is true that we are less often "getting into fights" from the perspective of our body/CNS. Fewer fistfights, certainly. But - can our bodies tell the difference between a barfight and multiplayer videogame combat?

In multiplayer games we find the exact experiences you describe as declining: Questioning manhood, dominance dynamics, and simulated conflict which I imagine feels similar to our CNS (but: without physical exertion so maybe not?). There might be more conflict of this type for your average 20-something man, than in previous generations.

Perhaps it is the lack of strength training and physical exertion that is the major factor.