* S3 is super expensive, unless you use Glacier, but that has a high overhead per file, so you should bundle them before uploading.

* If your value your privacy, you need to encrypt the files on the client before uploading.

* You need to keep multiple revisions of each file, and manage their lifecycle. Unless you're fine with losing any data that was overwritten at the time of the most recent backup.

* You need to de-duplicate files, unless you want bloat whenever you rename a file or folder.

* Plus you need to pay for Amazon's extortionate egress prices if you actually need to restore your data.

I certainly wouldn't want to handle all that on my own in a script. What can make sense is using open source backup software with S3/R2/B2 as backing storage.