The whole "applicable" part was a joke so sorry. But really, Rick Riordan didn't just pull the plot out of his ass, if the Titans or Giants (or both together) rallied their powers they could essentially over throw the Gods. Also Kratos (I think that was his name) literally killed most of the Greek Gods, save a few minor ones. Same goes 4 the Roman Gods as they are just slight reskins of the Greek Gods.