“You didn’t actually want to do X, here’s how to do Y instead” may indeed be helpful for the beginner who initially asked the question, but it’s very unhelpful for me who finds the page years later actually wanting to do X.
Stack Overflow isn't a site for beginners, it's for "professionals". At least, that's what all the Stack Overflow defenders tell me every time I criticize the snarkiness, rudeness and patronizing manner of many answers/comments you receive on Stack Overflow.
I'm fine with indirect, "question-the-premise" comments, but they should be posted as comments, not answers, because they are in fact not answers.