> If a storage server gets p0wned, the raw data could be deleted. That's true for every cloud provider.
It's not hard to create a cloud backup service where delete requires separate credentials which are not used in day-to-day operations (and so can be kept secure). And without these credentials a backup is kept N days and cannot be deleted or overwritten. Don't know if anyone do this, though.
Additional offline backups aren't really feasible past a certain data volume and daily change/velocity. I'd still encourage everyone to have them for their own essential data in addition to a cloud backup. E.g. by burning it to BluRay or tape (3-2-1 rule). You can see find my own, more philosophical discussion, of the topic here: https://docs.borgbase.com/strategy/. There I also distinguish between operational backups and archives. BorgBase is focused on the former. Offline backups are more suited for the latter.