Well, I don't have a problem with moralizing, necessarily. It offers a formula and theme for episodic storytelling, at least, and of course teaching people morals is a good goal. It's when the characters and situations feel artificial in playing out the moral that I get fed up (see so many superhero stories examining whether superheros should kill), or when (as you mentioned in your reply to lb_lee above) the universe bends over backwards to make doing the right thing work out. I consider AtLA to avert that last part, with Aang's dilemma against Ozai, because I felt both the Lionturtle and Energybending fit very neatly into the shape of the setting.

I'll keep DS9 on my Maybe list.