Why is the Bluetooth connection so weak on my Mac Pro 2019...

Why do I have difficulty with Wi-Fi or Bluetooth devices when USB 3 devices are attached to my computer?

Some USB 3 devices can generate radio frequency interference that can cause Wi-Fi and Bluetooth devices operating in the 2.4GHz band to have issues communicating with your computer. Here are some tips to avoid this issue:

• If your USB device has a cable long enough that you can move the device, place it away from your Mac—and make sure not to place it behind your Mac, or near the hinge of its display. The antennas for Wi-Fi and Bluetooth are located there, and USB 3 devices placed there might interfere with your wireless connections.

• If you're using adapters or dongles on a Mac computer with Thunderbolt 3 (USB-C) ports, plug them into the front port on the left side of your Mac, or into the ports on the right side (if your computer has them). These ports are the farthest away from the antennas, making interference less likely.

• To avoid interference on the 2.4GHz band using Wi-Fi, try using the 5GHz band instead. You can change this on your wireless base station. Bluetooth always uses 2.4GHz, so this alternative isn't available for Bluetooth.

from:

Using USB devices with your Mac - Apple Support

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It may be the fault of the other device in the pairing. Or does the MacBook fail to connect well with any device? I would recommend testing the connection with different devices. if you have already done so, you may want to check if the two devices are usually far away from each other, or if there is a lot of stuff ( e.i. a concrete wall) in between them.

Any external devices plugged in to ThunderBolt ports?

Apple works hard to keep the interference generated by their peripherals low.

Other vendors ... not so much.