I think it was absolutely essential the Saga conclude with him as it’s pretty much his story. Without Palpatine, this whole trilogy would feel like an unnecessary epilogue rather than a natural continuation and true conclusion.
Now of course the way his return was handled was carelessly sloppy. He should’ve been set up in TLJ and maybe even TFA, and should’ve clearly explained in TRoS that he is in his original body, and that he simply survived the Death Star. I don’t like the idea of him having died and returning as a clone.
I know most people say him surviving negates Vader’s sacrifice, but really, it’s about saving what we love, not killing what we hate. Vader saved Luke from Palpatine, not to mention putting the latter out of order for a good thirty years. Sure, he may not have completely finished him off, but he still did a damn good job.
Oh and Snoke being Plagueis would be dumb. Shoulda just been Palpatine’s apprentice, end of story.
If they had revealed he was alive at the end of TLJ, maybe it would have worked.