Can I eliminate specific folders from iCloud backup on my Mac Pro 16 inch?

If you have iCloud Drive Desktop and Documents turned on and there are folders that you do not want to sync, you can move them out of the Desktop and Documents folders. One option is to open a Finder window, use the Finder "Go" menu and click Home on it and then create a new folder in the Home folder. You can then use Finder and drag folders that are currently syncing to iCloud from their current location to the new folder.

Also note that Apple offers iCloud Backup for iPhones and iPads but not for Mac computers.

It is possible to sync data from a Mac to iCloud if you turn on those options (e.g., iCloud Photos, iCloud Drive including the Desktop & Documents option). Syncing has some of the benefits of a backup (and the benefit of being offsite) but is not the same as a backup. Major differences include the fact that not everything on your Mac can be synced and the fact that if you delete something, accidentally or otherwise, there is only a limited time period (30 days in most cases) during which it can be recovered.

Also see: https://support.apple.com/mac-backup

And more information on syncing in:

https://support.apple.com/en-us/HT204264

and

https://support.apple.com/en-us/HT201104