I never understood the "tribal warriors in starships" cliche of space opera.
Given how oppressive the Klingon Empire must be to the non-Klingons they rule, wouldn't a protracted war decimate the Klingon population because they can't count on their slaves fighting for them ?
Firepower based warfare with its emphasis on mass, regimentation, and efficiency renders warrior value systems obsolete. So logically the entire religion of Kahless would have fallen apart with the development of firearms and the Klingon Industrial Revolution. Unless, of course, like the Japanese a Klingon warrior society got a Lot of high tech from somebody else very quickly without having to acquire modern values. I read some Star Trek fiction that postulated that some more advanced race was impressed with Klingon warrior ferocity and gave them a lot of high tech in the expectation that they would be their pit bulls in starships. Big mistake.
Let's not get too simplistic in our classifications. There are different types of warrior cultures. The Klingon emphasis on personal honor and heroism, and a strong desire not to be disgraced in battle, avoids some of the problems identified in Arab culture. But Klingons do suffer some of the other problems, such as a highly centralized command structure that discourages individual initiative.
Even though humans started out technologically far behind the Klingon Empire, we eventually caught up with and surpassed them and for all intents and purposes defeated them (although that was glossed over by diplomacy and peace treaties). Just as with the United States today, the future Federation consisted more of professional soldiers than warriors, and it treated warfare as a distasteful but sometimes necessary task which should be executed in the most efficient and least-casualty-intensive manner possible.