Since we are discussing WHY younger generations are not feeling OK with locker room nudity, I want to drop a few cents of thoughts here.
I have this thought where any country/place with increasing violence rates past 50 years end up decreasing people's confidence among each other, mainly among strangers. With the increased sexualization of nudity, being naked has become an act of intimacy, even without any sexual activity involved. It's is harder for younger generations to get along like this because they learn much earlier about not trusting strangers, wich make them act more defensive.
This is why more people tend to only get naked among a small circle of known friends, colleagues or teammates.
Many European countries have lower violence, misogyny and homophobic rates, which generates less tension among strangers, so traditional nude activities are not a big deal, people do trust each other more. Though this varies according to big cities due to the diversity of cultures.
I don't think being naked will resolve the toxic masculinity promoted by sex selling industries all by itself. It just shouldn't be alarming or morally wrong to be naked in proper areas. Younger generations need their own time to understand that because they have a lot to unlearn from what's being hammered into their heads with either through religion, social media and porn.