Having said all of that, I’ll share my opinion.

If Palpatine was going to be brought back, there should have been some context setup in episodes 7 & 8. They didn’t have to foreshadow that he was still alive, but at least name drop him. Have a Resistance officer say something like, “at least the First Order isn’t as bad as when Palpatine kept the galaxy in darkness for 25 years.”

People have used the argument that these movies are meant for kids. Think of this trilogy from the viewpoint of a kid watching as his first Star Wars experience. He doesn’t know Palps was emperor of the galaxy, that he masterminded the destruction of the Jedi and the downfall of the Republic. He’s just some random guy never once mentioned or referenced in the previous two films who is magically pulled out of nowhere to be a bigger bad than Snoke. Luke does mention Darth Sidious once, but there is no context for a kid watching this trilogy first that Sidious and Palpatine are the same, master and apprentice, or completely unrelated characters. The characters all know what a threat he is, but the audience is never meaningfully informed. I consider that bad storytelling.