Not a real backup — no reliable way to restore
Dropbox Backup successfully stores data, but it does not reliably allow you to restore it, which makes it unsuitable as a serious backup solution.
I backed up a large Photos library (hundreds of GB). The backup clearly exists in Dropbox, but there is no practical way to retrieve the full original data:
• There is no functional “Restore” option available.
• Web downloads fail due to undocumented limits (e.g. ~250 GB / file count limits).
• Even when downloading smaller chunks, many original files are missing (in my case, the bulk of JPEG originals).
• Support initially gave misleading advice, then ultimately dismissed the issue rather than solving it.
Dropbox advertises this product as an alternative to Time Machine, but unlike Time Machine, you cannot reliably get your data back. A backup that cannot be restored at scale is not a backup.
This product may be acceptable for small, casual datasets. It is unfit for any serious or archival use.