I think the idea of a ST would have worked much better, if they had introduced the idea of a hidden Sith home world from the very start, the root of evil so to speak, an anti-Ahch-To, where Palpatine and Sith from the past are sort of a physical manifestation of the dark side in the known galaxy, that has its roots on this hidden unknown planet, where the spirits of the Sith of old reside, and can still take physical form, a sort of Mordor in the Star Wars galaxy so to speak. The OT would thus be the culmination of Empire vs rebels, and the fall and redemption of Anakin Skywalker arc, while the ST would be a culmination of the Jedi vs Sith war, that ends with the destruction of the Sith home world, and its corrupting influence on the galaxy.