In an edit which removes Rey Palpatine, I agree that her story would feel even weaker than before. However, you could keep Rey Palpatine as a misdirection to get her to go to Exogol. Take out the flashback to her parents getting killed and Luke’s insistence that Leia knew all about this, and add some Emperor dialogue revealing the deception. His statements later actually support that conclusion anyway, where he refers to her as merely a scavenger girl.

Now Rey has to come to terms with a possible unavoidable darkness and it doesn’t trash the rest of the ST in the process.