I can understand the attraction of moral simplicity.
But when the main metaphysic of a fiction is built on a moral premise, if that premise is too simple, you quickly explore the entire premise. A longer-running franchise needs to have more space for exploration of its own themes, and absolutism doesn't have that space. It'll hold up for a movie or three, sure, but then you're done.
This is precisely why the larger SW universe had these alternate views of the Force - because the super-simple Jedi/Sith dichotomy has limits to its theme potential.
Firstly, the moral fabric of the setting’s magic isn’t the only facet of the setting that can be explored. Each new story doesn’t need to explore new facets of that magic, much less specifically new moral facets.
Further, the concept that the Force itself if Nature, and the Dark Side a corruption of Nature, doesn’t mean there aren’t moral facets to explore. The OT explored redemption, hope, and faith in others. The PT explored destiny vs free will, and how one falls, and the danger of letting yourself believe that “maybe Evil isn’t a real thing, but maybe is just something the Establishment made up to keep you in line.”
The ST seems to be exploring free will from a new angle (vs the weight of the past), the danger of viewing things like empathy and attachment as weakness (Kylo’s whole thing), and the separation of cosmic moral ideals from the realities of organizations in conflict, and the impact of protracted war, even when the cause is just.
Because the morality of Star Wars isn’t binary, it’s just the Force that is. But the Force doesn’t care about morality in the same way we do. We KNOW that with absolute certainty because Anakin is redeemed. The Force isn’t moral like a human is. It is a “Good” Force of creation, life and death, natural order, and cosmic harmony. It’s space Druidic magic, and The Dark Side is space necromancy.
Edit: also, forget the Jedi and the Sith. Even in new canon, there are more philosophies than these. And in canon, they either abstain from any use of the Dark Side, or eventually fall to the Dark Side and become corrupted monsters.