Icloud very VERY slow to sync files

I have a similar but different problem. I don’t want to highjack your thread but I didn’t want it to just die in the group either. Here is my post. Macbook Air with iCloud Upload Sync Probl… - Apple Community

It seems to me that if you are paying for iCloud, you should be entitled to phone support to solve your problem. I am only working with the included 5GB. I hope you get some resolution.

What are you referring to when you say "we rely on USB drivers"?

iCloud is as fast and reliable as the slowest link in your Internet connectivity. Slowness can be caused by your WiFi, your ISP, the Internet circuit speed that you pay for, or VPN providers that you may be using. It is however not due to Apple's iCloud infrastructure. One other issue that can cause slowness is any security software, anti-virus, or VPN software that you are using.

In the case of security software or antivirus, those should be removed as they provide no benefit to the Mac. If using VPN software, test with and without it.

When in doubt, always test using a wired Ethernet connection.