GPP is no way overrated. Their uses can vary over the game and that can be argued, but to say Great Person Production is overated is silly.
Not to say you cannot win without it, You can with without a strong GP farm, but your game is more power with one.
Regarding Pacifism, the really good players know how top use it at higher levels of difficulty (Immortal, Diety). Unfortunately I do not (Monarch and Emperor) unless I am playing a Spiritual leader and can severely limit my military (great diplomacy or isolated). Still good food for thought, perhaps I will try and force myself to use it next time.