I am convinced Palpatine could have been resurrected for the Sequel Trilogy in an intelligent, narrative-serving way, but it would have required meeting four conditions:

Explain how in the film itself. Audiences saw him fall down a pit and explode in a moon-sized station that also exploded minutes later; if you’re going to tell audiences that wasn’t his end after all, then audiences are entitled to be satisfied that it makes sense before the credits roll. Passing off a question this fundamental to inference – in effect making audiences do homework simply to understand the story (whether in the form of reading supplemental material or piecing together a headcanon explanation themselves) – is just sloppy, lazy storytelling that disrespects the audience.
Reveal him early enough that he feels like he fits in the trilogy as a whole. My preference would be to at the very least hint at him in VII, but he would’ve had to be revealed no later than VIII. But by Episode IX, it was too late to do it without making the ST feel disjointed. Lucasfilm desperately needed an adult in the room to give Palpatine a hard veto, to tell Abrams and Terrio that the character had simply missed his window.
Confront the Chosen One ramifications head-on. Like it or not, the prequels gave cosmic, borderline-theological implications to Palpatine’s death. If he never actually died or was only briefly dead, if the Sith survived and continued planning in the shadows just as they did before The Phantom Menace, then the prophecy was wrong in some major way. Either Anakin was not the Chosen One, there was no Chosen One, or the balance it foretold was far less significant than its prophesized status would lead one to believe.

Now, this does not mean it couldn’t or shouldn’t be done, but it does mean the story has to take responsibility for the fallout of the decision – and no, giving Anakin one “bring back the balance” line doesn’t cut it. The idea that balance is never permanent and must be continually maintained is a good one, but is suggested so fleetingly that the line simply doesn’t suffice to account for the sheer scale of the retcon.

But it didn’t have to be that way. A differently-structured ST could have not only navigated this minefield, but done so in a way that enriched the PT rather than undermining it, by making the question of prophecy and the old Jedi Order’s reliance on it one of the new trilogy’s major themes. The groundwork for such a development was already laid in Revenge of the Sith, what with Yoda himself warning that the prophecy “misread, could have been.”

Have Luke and Rey discuss and debate whether the prophecy was correct, whether Anakin was the Chosen One after all, what “balance of the Force” even means. Have Anakin return as a Force spirit in a larger role to add his insight to the discussions. Hell, you could’ve even had Palpatine play on the heroes’ doubts by claiming to have created the prophecy to goad the Jedi into training the instrument of their own destruction. All of this could have given the ST some much-needed philosophical depth by diving into the question of predestination vs. free will, and brought things full circle by highlighting a failing of the old Jedi Order from which Rey and her eventual students could learn.

Finally, when you have a character come back from the dead in a story that’s meant to be a true ending rather than another midway point, you have to make clear why he can’t just come back again. John’s amazing Force Ghost edit achieves this in an elegant way, but absolutely nothing in vanilla TROS does. There is nothing in the official film that would prevent future storytellers from revealing that Palpatine had another supply of clone bodies to escape into stashed on Korriban, Malachor, Vjun, Wayland, or some other Sith planet that hasn’t been made up yet. Hell, nothing in the film even rules out the possibility that Palpatine’s spirit is already lurking inside Rey!

I sympathize with the desire to bring Palpatine back. I enjoyed and accepted Dark Empire back in the day. Ian’s magnificence in the role was one of the things that had me desperately trying to convince myself that I liked TROS as I drove home from the theater. And I have come around to the conclusion that it could have been the right decision for a different version of the Sequel Trilogy. But he simply didn’t fit with the Episodes VII and VIII we got, and the Episode IX we got botched the execution on every level.