This is an abstract response to a concrete demonstration of usefulness. Of course, if I'm writing crypto code or something where I don't understand the domain well, relying on Copilot would be foolish. But for a well-defined problem like the one I faced, juggling tree representations and a little recursion, being able to specify what I wanted and have the machine generate the code was actively useful and did actively save time. Also, don't you read your code once you write it in the first place? IF you've written it, you know what you meant, and are more likely to read something you didn't even write there, whereas if you're checking over the shoulder of your computerized coworker who has no ego to get hurt, you can be as critical as you need to.