Raid is not a backup :( For the really important data (photos, documents, ecc) a small 1GB raspberry pi + USB external HDD works great as a Borg server for daily backup, there is no need for a full NAS when you can store all important data in less the a handful of terabytes
I’m not implying Raid 5 on its own is a complete backup.
Within a storage array though it does provide redundancy at that level, and generally speaking most people don’t access a raid or NAS at a shell level only where they drop rm -fr’s
Separate and offsite backups are non negotiable, however running a raid 5 locally can greatly reduce storage rebuild/restore time, if a single drive fails the rest of the raid continues to work fine until replaced.