Their introduction and the whole explanation for the mystery brings about what could be some very interesting moral dilemmas that never get explored. Finally, we have the episode's protagonist act irrationally and against his own self interest to help his new alien friend, everything works out in the end, with the exception of the moral dilemmas being completely ignored.

What would you like them to explore?

Disclaimer: I'm a big Star Trek fan, and my favorite series is DS9 because of the moral ambiguity.

To me, that episode was about hunting and the moral dilemmas of hunting animals. But it could be about any situation where the prey has accepted their fate, even in a human context because of social acceptance.

That episode first gave the perspective of the hunted, their actions and motivations. It opens the question. How would you behave if you were in a class that was hunted? Tosk was skittish, distrustful, secretive and non-assertive except when the Tosk thought it might get in more trouble. Those are probably traits many would adopt if they were hunted.

Then it gets revealed why the Tosk was behaving that way. Another class of the aliens was hunting Tosk.

That custom was foreign to the crew of DS9 because class and species differences were supposedly eliminated by that time.

It's still common in our time though. People hunt animals and marginalize other people.

It didn't seem at all odd to me that O'Brien acted against his interest to help Tosk. People sacrifice their self-interest to help animals all the time. They sacrifice even more if the hunted class are people, like the Jewish people in the time of the Holocaust. O'Brien saw Tosk as another person, not a dispensable creature because he wasn't in a culture that saw hunting as socially acceptable.

The ethical line that gets drawn when people see other beings as animals or beings like themselves is also an ethical question.

It's an interesting thought experiment to wonder why more people didn't hide Jewish people during the Holocaust.

It has implications for what happens today. If people can see other people as enough different from themselves, they can care less about them. People of different religions or races can be marginalized or treated differently.

The writers of DS9 couldn't explore those moral ambiguities explicitly because once a real life context was given, not in the form of a metaphor, the viewer is likely to revert to their view of the socially accepted view of the moment and not explore the possibility that there might be other ways of looking at things.