The Matrix is an often used example, but for me it’s the Alien Prequels - especially Alien: Covenant really makes the Original Alien much worse. When the original was released in 1979 it had the perfect Monster. A dangerous killing machine of unknown origin. The missing background of the alien is a big part of its scary mess. It’s a blank space in its mythology that the viewer can fill with many explanations. As these explanations are not precise they don’t have to be logically coherent.
Covenant (and to a lesser degree Prometeus) wanted to fill this blank space and tell us the aliens origin. But once you fill out this missing piece of information it is fixed and can only be one piece. There exists now only one singular explanation. And its a boring: The Xenomorph is basically a creature with it’s origins on earth (because David, who’s origin is on earth created it).
I find this hugely dissapointing. The biggest dangers of deep space are all human in origin is extremely small minded.
(Star Trek: Beyond had the same boring plot - the mysterious villain turned out to be a human after all. As if only humans are capable to pose (or create) a serious thread to humans.).
What are your examples for franchise-movies that somehow made the original worse?
I’ll go ahead and pile on with the others here:
In the original trilogy, one is given to believe that the Jedi were a good and noble order who were betrayed by Darth Vader and then hunted down by the Empire.
In the prequels, it is revealed that they are a bunch of idiots who can’t see what’s happening right in front of their faces with Anakin falling to the dark side, and who are so wrapped up in politics that frankly they deserve to be destroyed.
You don’t have to be a telepathic precognitive to see that Anakin was going down a really dark path. Anyone with an ounce of human empathy could have had a thirty second conversation with the dude and seen that he needed therapy and stability. But instead the Jedi sent the human equivalent of a tanker truck full of nitroglycerin right on into the wars, and then when that went poorly we’re expected to believe that it’s some kind of tragic fall, rather than just piss poor management?
On top of that, the Jedi were emphatically not the “guardians of peace and justice” that Obi-Wan made them out to be in Episode IV. They were loyal to a corrupt and decadent Republic that was not serving its people’s needs. The Separatist movement never would have gained momentum if there weren’t real problems in the galaxy that the Republic was failing to address. But when violence broke out, rather than trying to arbitrate peace and justice, the Jedi became generals fighting at the head of an army of child soldiers.
Virtually every good quality about the characters and systems in the galaxy stated or implied in the original trilogy is invalidated by the prequels. They will stand, possibly forever, as textbook examples of how not to expand on an established universe.