The friendzone, while arguably real, is generally still used as a petty excuse for Nice Guys who don't understand why being nice doesn't entitle them to affection. NiceGuyism and friendzoning go hand in hand in that regard.
Basically getting friendzoned means a guy has generally failed to act in a remotely attractive way or find the courage to be the kind of credit to humankind that women prefer, and wants to blame it on women being incapable of seeing him romantically.
In essence, it's asking oneself, "why isn't she attracted to me?" when the real question is, "why am I so unattractive?"
The reversal, for girls, is known as floating mirthlessly in the Brozone Layer, and it's about as rip roaringly hilarious a spectacle as it is just plain sad. Notice this is different from friendzoning for guys, which is not hilarious because it got well past the point where it was just downright creepy self-victimization a looong time ago.