Has someone broken into your home, removed your books, and put new books into their place? Has someone hacked your computer and switched out your pdfs? Did someone cast 
modify memory on you to alter your memories of the lore?
No?
Then your stories 
aren't being replaced. You still have them. You can still think about them, you can still read them, you can still play them. You may not get much 
new stuff you didn't like, but think about all the people who didn't have much 
old stuff that they liked. I mean, you just told 
@teitan that you wish you didn't have to ignore "just about all of" the new canon. If I were running in the Realms or Greyhawk or Dragonlance, I'd have to ignore just about all of the 
existing canon to make a setting I like. I had to ignore about half of the canon in Ravenloft, and I 
love that setting.
Ad all of those stories have had huge rewrites. Star Wars is now ignoring the EU, despite the outcries of the fans. When Roddenberry started up TNG, he deliberately ignored everything in TOS except for the movies and a couple of species, and it took a long time to start bringing in some of those old elements back. It took until Enterprise to remember that Andorians and Tellerites, and I think Orions, still existed. And Star Trek is 
famous for ignoring its own continuity and rewriting huge parts of it (remember living through the Eugenics Wars? And Worf doesn't want to talk about what happened with the Klingons. And neither does the 
Discovery crew.) 
And there's the Abrams Trek. Marvel often ignores, rewrites, and blows up its own continuity.
And, of course, DC had 
Crisis on Infinite Earths (and 
Infinite Crisis--which always gets my Dad annoyed, because it should be 
Crises--and New 52).
Edit: I really gotta stop starting my sentences with the word 
and.