[randomdata]

> product types are the wrong shape for several different problems

While that is true, the shape has no bearing on the handling problem. Go could have every type shape-defining feature ever conceived and it would still have the very same handling problem – for errors and everything else.

> Errors are an example where it's more obvious to more people.

In my experience, the vast majority of bugs I encounter in the real world are related to the handling problem of non-error values. That is where it is most obvious, and not just in Go. I expect errors only get talked about because it is fashionable to repeat what someone else said, not because anyone put any thought into it.

> Also the machine actually does know about error

Only within the confines of one human interpretation of how the machine functions, just as is the case for code. The machine itself has no such concept. It doesn't have awareness that a given state is an error or a rainbow.