I too am experiencing extremely slow uploads using verzion cloud. I am uploading pics from my iphone 12 pro and it takes about 30-45 minutes to upload one picture now. At the start it uploaded about 80% of my pictures within just a few minutes. Then uploading slowed to a near halt and I have only been able to upload 23 pictures in the past day and half.
Verizon cloud is a big failure in my view and is part of why Verizon charges so much for their data plan for 5G.
You are better off using Amazon Cloud for storage of pictures/videos; it works great, fast, and seamless.