RAID is for continuous of operations, backup is for restoration after a failure.

I have both, but run Raid-6 on my array due to the size of the drives. As has been observed here, if one drive fails and then another drive fails during the rebuild, you’ve lost everything.

Then to add to that I’ve got backups of everything I can’t replace. Plex library will come back automatically (though it will take a while). But my documents, digital filing cabinet, pictures, videos of my kids, those are all protected by raid, backup, AND off-site replication.