Retcons can't change what you read in the past, but they can most definitely change how you perceive those things and how valid you consider them.
For example, I can read the original version of The Hobbit, where Gollum freely gives away the magic ring like it's not really that important. I can still have read that. But thanks to Tolkien's later retcons, I have to know that this version is not true, that in the story, this was a lie told by Bilbo so Gandalf wouldn't think this magic ring was THE ONE RING.
I can read Sherlock Holmes 'The Final Problem' and enjoy his death, but just be aware that he didn't actually die, thanks to later stories.
Continuity, like life, is full of mysteries. Stuff that's left unexplained can be uncovered, and new knowledge can always change things.
You are taking a very literal approach to things, you need to be way more flexible, not everything has to be as it first appeared.