I dismissed it as "they probably developed it for Chrome" and then used the inspector to set background to white. I can't imagine how this is not a bug.
I don't find it to be "nearly unreadable" myself, but yes it's difficult. I think it depends mostly on the quality of your monitor, and on how it is calibrated.
It's the contrast, or lack thereof. Black text on a gray background is going to be hard to read on any display.