Klingons become quite popular after their rework in movies so from TNG onward you can see increasing amount of fanservice for them. Despite being archetypical enemy of the Federation, a warrior culture vs the peaceful one, we see central characters like Picard or Dax being basically honorable klingons, and there is not many klingons actively opposing that despite their society is xenophobic as fuck. Also they get whitewashed all the time with all the talk about honor, but nobody talk what is exactly happening with multiple species conquered by klingons, we never see them.