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.