I think if they felt Palpatine had to return in some form, I would’ve preferred the conflict would’ve centered around a Sith cult trying to resurrect him, and the protagonists are trying to prevent that
Having only seen TFA, wouldn’t have been better/made more sense for Kylo & the Knights of Ren to be up to this in the 2nd film & then conclude it in the 3rd?
This seems to be the way to do it & I gather this isn’t what it was done.