Yes, the older ones of the rotating backups are still readable.

But that's not even the actual problem nowadays: CDs and DVDs were nice when their size was still relevant in comparison to usual amounts of data. The real problem behind their decay is that we are lacking a widely available, properly scaled backup solution for more than a decade. So the mean reason people have now unreadable optical data is that they stopped thinking about it a long time ago for an utter lack of options.