Is traditional masculinity harmful?

No it's not harmful because a lot of people confuse aggression with masculinity when aggression is actually thinly veiled insecurity and isn't an alpha trait. A true alpha male would be dominate by being assertive and not aggressive which is two different mind sets. Assertiveness comes from confidence while aggression comes from insecurity. Aggression can also come from fear and neediness.

Males, like females are sort of forced into gender roles so as a result insecurity comes out as aggression more of a learned behavior because insecurity is seen as feminized.

There's nothing wrong with traditional, then again there's nothing wrong with new age relationships as well because a lot of what people see as alpha is not really alpha to begin with.