And what percentage is work that should be done, let alone that needs to be done?

I have been told that is the wrong metric to use. You're supposed to look at how much faster it's getting better, and then just draw a line and assume it's always going to continue that trend. Okay, so it took them 70 years to get to this point. Imagine what they can do with another 70 years of development. It might even generate comments that are proper for the programming language you think it's supposed to be generating.