Why upload speed is so slow?

My monthly Internet plan is 100mbps.

The actual download speed is around 115mbps but the upload speed is merely 4mbps, that is only 3% of what is claimed to be. I understand that because Comcast use Coaxial Cable to transfer data so upload will be slower than download but a 4mbps is unacceptable speed! The competitor provider Verizon provides fiber optic and their down/upload speed is equivalent.

When could Comcast fix the upload speed problem?