Disclaimer: After how many words written about Fanfiction, you STILL want to think I own Harry Potter? Fine, I don't own and never will. (As if I'm that calibre of writer who COULD write something that good.)
Dear Astoria,
Even with the old pureblood families in decline (and let's be honest, they've been in decline for a long time), we'll always have something that's ours and always ours. It's something that we overlook and some of the more snobbish pureblood families look down on, but we'll always have Hogwarts.
Yes, I know that it takes muggle-borns (and has the occasional rat), but it is the main school for magic in Britain. Practically everyone goes to Hogwarts, regardless of background. It's something that has survived every challenge thrown at it and come back stronger for it. If nothing else, Hogwarts will keep wizarding culture alive long after everything else has turned to dust.
Well wishes,
Your sister Daphne