I don't really have a problem with the low tech, provided that it's an active choice rather than implied laziness.
Weapons never exist in a vacuum. You develop a weapon, chances are the other side will either obtain a copy or steal one. An arms race is fairly inevitable.
Briareus the hundred handed giant with knives is bad enough. Briareus with AK47 (or equivalents)... not a good idea...
Plus it's possible that the more complex the weaponry, the more of a foothold Ares (as God of War) has, and that's never a good move.