Personally I was intrigued to see the Emperor return after the first teaser. To see him achieve the power to cheat death. And the actual way he’s brought back is a really interesting concept.
I mean think about it, 30 years after his death and the fall of the Empire, a group of Sith cultists, hidden on an uncharted planet, finally manage to perform a twisted dark side ritual that allows him to come back and possess a decaying body.
He wakes up to find a raging war between two new factions. The First Order see him as a threat to their power, and the Resistance obviously can’t allow him to return…
To me the thing that totally ruined his return is that they decided to connect him to Snoke, Kylo and the First Order, the idea that he’s “been out there all this time, pulling the strings”. It hurts the ending of RotJ because it implies Palpatine immediately went into concocting a plan to override our heroes’ victory. He’s the one that turns Ben to the dark side, he’s the one that creates the First Order, and our heroes are completely oblivious to the fact Palpatine’s behind it all!
Most people point to the fact he wasn’t set up at all in the first two films, but the truth is he didn’t need to. If Snoke had a completely separate story to the cultists on Exegol, making him the main perpetrator of everything that transpired after the fall of the Empire. If Palpatine had been completely out of the picture for 30 years, his return wouldn’t actually need previous setup. It would have elevated the stakes as a third faction rises from the shadows. Instead as it stands now, it only undermines the previous two films, since Snoke stood as the big bad evil perpetrating everything. His eerie mystery in TFA, his power and manipulation in TLJ. The man who built the First Order, who turned Ben to the dark side, who orders the destruction of the New Republic, reduced to a mere puppet with no agency in the story at all.
And then there’s “Rey Palpatine”, which I don’t even need to get into, ugh.
The point is Palpatine should’ve been treated as a new threat, instead of bending (and breaking) the story to insert him into everything that transpired in the previous films.