I'll bet that if it really was important you could pay someone (LLMs make this easier) to dig through the data byte by byte and get everything back despite the corruption. It would take years, and be very expensive, but typically there is enough redundancy to figure it out. Often you only really need a small subset of the data and can live without the rest.

Don't get me wrong, drills are important! You should do them. However backups without a restore drill better than no backups at all. Even if you only get the last full backup, the data from the last 6 months will be the easiest to recreate from scratch if you must.