The nature of ditch digging is such that given enough effort, it's probably still possible to dig a ditch. It doesn't mean you'll be motivated to dig the ditch, it doesn't mean it won't be ridiculously hard to dig the ditch, but barring seriously physical issues preventing you from making progress, digging a ditch is mechanical and doesn't really involve a serious need for critical thinking.
When you burn out as a software dev (and probably other fields that involve serious mental investment), it doesn't matter how much you try, there's a good chance you'll just fail.
I do agree that software development is not the only field that can be seriously impacted by burnout, but the degree of impact seems to be highest in fields involving knowledge work.