It’s really important that you NOT consider iCloud a backup. That is not its function and it’s not what it does.
A backup is a snapshot in time that one can return to to recover data.
iCloud is file synchronization to the cloud and that sync is shared to all of your subscribed devices.
If you delete a file from a synchronization like iCloud, the file gets deleted from all devices and the cloud.
A backup remains as that frozen moment in time, while synchronization is an ongoing and changing thing.
iCloud does offer file recovery for a span of 30 days, but if you deleted an item 31 days ago it is not accessible, whereas a backup would still be available to you.
An additional reason to not think of iCloud as a backup is that it is limited in what is synchronized. It synchronizes your Desktop and Documents folders, and if enabled, certain other data types when stored in the appropriate places (Keychain Access, Photos, Music). Anything not stored in those places is not synchronized and not available to other devices, or the cloud.
Many of us have photos stored in the Pictures folder in the Home folder, that are not in the Photos app. Those photos are not part of the synchronization that iCloud offers. They exist on the storage of the device they are on.
If the purpose is an actual backup and not synchronization, please look to Time Machine or one of the other solutions out there that will provide a complete and recoverable backup.
Hope this helps!
B