I go back and forth on this. In terms of general thoughts, I definitely dislike this, especially when it comes to a franchise like Star Wars where you hear about how the ST undoes the OT… and yet the old EU did that on a pretty consistent basis with new empires, new superweapons, Sith and so on. ESB in a way could be argued undoes ANH as that movie was designed to be one solid movie and yet ESB shows the Rebels are in a terrible state after that film. I personally just don’t care in the slightest about if things are undone or “ruined”. To me, I care about the story.
That being said? I do feel that in order to do this properly, we need to have the story feel like it’s actually continuing from the previous films. I think TFA and TLJ did this very well overall and to an extent upon reading it, it seems like DOTF by Colin Trevorrow looked like it was gonna do the same… but TROS hurt it by bringing back Palpatine and transforming the story into being this overly grandiose, friggin’ ridiculous display where it’s about the Jedi being destined to take down the Sith again when they haven’t been relevant to this story for two whole movies and it undoes Anakin’s big moment because yes, he only did it to save Luke… but it’s more than that. If we are to count the prequels? This is supposed to be a personal achievement for Anakin for after years of being under the oppressive thumb of the Emperor, the old man who groomed and manipulated him into being the Dark Lord of the Sith that helped to bring about the end of the Jedi, the man who made him believe this was all he had left, he finally is shown by his son that it’s never too late for anyone and so he’s able to get the strength to make things right and overthrow the Emperor once and for all with the ST being poised to be more about the legacy of the Skywalkers and the old heroes who lived in the era of them. TROS then comes along and oops! Palpatine had a convoluted back-up plan as per usual and now that big personal sacrifice and achievement means absolutely nothing because a rushed production meant fanservice galore instead of telling an actual story.