I would argue that Obligation nor Duty encompasses what it means to be a Force user. They can carry both Obligation and Duty, but neither of those is personal. Both of those deal with how they relate to other people. Morality is inherently personal. The Universal Force is concerned about how the individual deals with its powers, not on how that individual relates to others. The Force is not very relativistic in how it views Morality, though in our times the term morals is certainly skewed by relativism. Mixing in Good with Evil while dealing with Morality makes a lot of people uncomfortable. I can appreciate that. I can assist my players struggling with that at my table, but it can be something very personal and relies heavily on motivation. The same action by different people in differing circumstances can be good or evil. This makes people afraid to make a judgement and therefore Morality becomes a way of judging a character and our modern approach tends to not like to do that. Especially when compared to a Morality of a Truth (capital T), instead of the morality of an individual which can be subjected to relativism.
I don't think my way is the only way. I try to avoid most of these Morality threads as there is a vast difference in experience and perspective among the readers. I will allow others to fully vent their opinion without taking offense, but do not feel that this is reciprocated by most. I would dare say that without stating it, religion has influenced most of these discussions and we have all avoided it because we know where that will take us. It is still an influence on how we view this kind of touchy subject. I don't have an answer that would suit everyone, but I firmly believe in the power of this mechanic and where it can take characters in their development.