Yes, it is unfortunate. Information loss on the internet is not limited to CL, however, and many of my bookmarks became stale over the years. When I encounter a "treasure trove" of information, I make sure to archive it on my machine (and ultimately on backup hardware). Sometimes I put it up on sites like GitHub.
In fact, it loks like it’s inaccessible now, at least in my browser. Google does have some pages indexed though: https://www.google.com/search?q=site%3Aalu.org