I think the problem is the way that millenials are viewing these characteristics. They are viewing them in "black and white terms" and taking it to the extreme. In other words, you're either selfless or selfish; strong or weak; socially engaged or socially isolated; independent or dependent.
I really think its a wrong way to look at human traits, and, instead prefer to view human traits on a continuum, often determined by the environmental context, which often dictates how one is going to behave.
I mean, in some contexts, it's fine to be selfless and in other contexts, its fine to be selfish. You're likely going to be more softer and gentler when playing with your 3-year-old child, compared to if you're at the gym trying to bench press 450 pounds. You're likely going to be independent when performing a job at work, but may need the assistance of others and depend on someone else's expertise. It really all is determined by the context.
I do not know why the millenials are PURPOSELY ditching certain human traits in replace of other traits. A psychologically healthy individual can modify their personality depending on the context and act accordingly when needed. These millenials take everything to the extreme, to the point of omitting that what makes us human, even the so-called masculine traits or however you want to define them. What you're left with is unstable minded millenials who cannot adapt to their surroundings, as they are so fixated on ditching X trait for Y trait.