Time Machine back up taking almost 24 hours for a 2 TB Mac

Definitely erase the drive and start over. You may wish to consider adding at least one more backup disk to Time Machine. One and only one backup device does not comprise a robust backup strategy. TM will back up to as many of them as you wish to provide. Despite its mathematical inaccuracy "two is one and one is none" is an applicable philosophy to keep in mind with backups.

After erasing, Time Machine may bug you that it cannot find the previous backup disk — the one you just erased. Just remove that one from its Settings.

You should also remove the "WD Drive Utilities" software from your Mac. Drive manufacturers are fond of bundling various and sundry "free" software with their drives. They're not worth the price. They are all unnecessary and they often cause problems. An earlier version of that specific product was notorious in the distant past for spontaneously erasing perfectly good hard disk drives — another reason to have more than just one backup drive.

Follow its uninstallation instructions.

you skipped a step when you set up your backup drive initially.

Drive makers often provide proprietary driver software to "save you trouble" when setting up a new drive. They initialize the drive to the most commonly-used format, and ask you to install their Utilities.

But because Windows systems outnumber Macs, the most commonly used format is Windows New Technology File System (NTFS).

Windows New Technology File System (NTFS) is Microsoft proprietary.  Without added utilities, the Mac can not write to NTFS drives as issued. If you install WD Utilities, the drive KEEPS NTFS format and creates a Mac Volume-in-a-File (Sparse Bundle Disk Image).

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The Best Practice is to ERASE that drive by its immutable manufacturer-given DEVICE-name when new, and NOT use the drive-maker's Utilities at all.

<< So to clarify, I should have the NTFS utility running? >>

When the drive is new, drag the driver makers Utilities to the Trash and empty the Trash.

We occasionally see drives fail when they were not ERASEd when new, but the drive-maker's Utilities, including Paragon or Tuxiera NTFS Drivers were installed. All proceeds fine until that Driver is not included in the MacOS image being used, or a modest failure forces you into recovery or Installer system, which has NO add-ons available. Then the drive 'mysteriously' stops working.

The right way to do it (new or old) is to ERASE and start over.

If you have whole lot of essential and unduplicated data on it, that would be WAY more complicated.

But it's a backup drive, right?

Yeah, just ERASE the Device by its immutable manufacturer-given DEVICE-name and start over.

The disk above is identified as a Physical device connected by SATA, with Device-name shown above (certainly not a name I gave it). Since has an older system is on it, it has all the APFS data structures showing in "View all Devices".

CarolinemanD wrote:

Oh, just saw this. Thank you. I'll check this out.

To keep users from being confused by the added complexity of Apple File System data structures, Apple's default presentation currently omits all references to the underlying Physical Device.

As you can see in that Apple article, to initialize a new device, you MUST expose the underlying Physical DEVICE by changing the tiny 'View' menu to "Show all devices".

Failure to ERASE the Physical DEVICE by its immutable manufacturer-given device-name is what leads to problems later. The default view show only Volumes, not DEVICEs.

This Apple article explains how

https://support.apple.com/guide/disk-utility/erase-and-reformat-a-storage-device-dskutl14079/mac