Major changes: an increase in the consumption of processed sugar, fat, and carbohydrates. Mainly: snacks, junk food, candies, sodas, and bread products. This is unprecedented in human history and has various negative effects on both males and females.
If testosterone is down it's likely due to an increase in unhealthy lifestyle choices which involve those foods and more sedentary lifestyles. Basically: lifestyle choices are rendering high testosterone levels to be unnecessary for the male body to maintain.
Someone at some point mentioned soy: it's high in estrogen. You shouldn't feed a boy soy, it leads to gynocamastia (male breasts) for some. It's standard knowledge if you're a mother of a lactose intolerant child (btw). I learned this by researching caseine and lactose low diets for 2 of my kids when they were struggling with a health issue in the past. Things like almond milk were given temporarily instead.
Life is soft for the modern HUMAN living in a 1st class society. Male or female: very few people have ever had to tough it out.