Honestly I don't think the theory is that bad, considering what we have seen it's very odd that a 530 pound, super fast, super strong, technologically superior and better trained warrior species gets it's butt kicked by a single human in every movie, I think the theory makes perfect sense. They just are not the best the species has to offer and that is why they end up losing every time. Then again, they take out multitudes of humans before being taken down by the prize human so it's not like they haven't proven their worth and power and skill in every film. So it could go either way.