Palpatine has eclipsed all other discussion of Star Wars: The Rise of Skywalker. It is impossible to discuss the film following that first trailer without bringing up that laugh, the vision of the Death Star dish laying broken on a planet's surface or Ian McDiarmid appearing on stage at Star Wars Celebration, cryptically smirking at the audience.
It is not unreasonable to assume that Palpatine's return is somehow Disney trying to make up for Star Wars: The Last Jedi. Many fans see its themes as antithetical to the Star Wars saga as a whole. They feel the idea of letting the past die runs contrary to everything the series stands for.
These people also are objectively missing the point of The Last Jedi... and, indeed, might be missing the point of what Palpatine's return represents in the greater Star Wars mythology.
"Let the Past Die" Isn't The Last Jedi's Message
There are two core themes at play in The Last Jedi. It seems apparent that Star Wars: The Rise of Skywalker will build upon both themes, but in different ways.
The first theme is that we learn from failure. Yoda very bluntly says this in his small, memorable scene. It is the mentality that guides the whole plot.
Everyone in The Last Jedi fails in some way, and the characters are forced to develop beyond that failure. Finn and Rose fail to complete their mission, thus putting the Resistance at risk. Poe fails to be a worthy leader and helps almost ruin the Resistance. Rey fails to realize that Kylo cannot be saved, thus putting a worse madman in charge of the First Order. Luke fails in his inability to resist the pull of the Dark Side that has been tugging at him all his life.
These failures result in everyone becoming stronger characters in their personal journeys. When The Rise of Skywalker starts, these characters have emerged from their lowest points as better people, capable of defeating the First Order once and for all.
The second theme, however, is that the past isn't great. We can't keep repeating the cycle of the past. In order to truly grow, we must move beyond it. But at the same time, the theme isn't "let the past die," so much as it is "grow beyond the past."
It's very telling that the only characters who speak about ending the past are either Kylo Ren (who is the villain) or Luke (who realizes he was wrong). Yoda, again, states this theme perfectly: "We are what they grow beyond."
So, how does Palpatine tie into this?