I think the entire first two finished and released chapters of the trilogy are more relevant than Lucas’ original ST ideas when discussing the merits and failings of the third chapter in said trilogy. Palpatine’s return was not setup and doesn’t contribute to anything in the story that was build up through TFA and TLJ, he was not relevant at all and the Sith were intentionally left behind aswell. However their importance in TRoS cannot and should not be downplayed so I’ve been mostly discussing for the best implementation of Palpatine possible in the film, to which I think keeping the “all the Sith” aspect is essential. If anything I think it works to heighten the spirit transfer/clone bodies stuff to show how his body and mind are separate.