I think the whole point of critique (esp. in this particular case) is to provide feedback. In both my and the OP's mind, the shirt was created with at least som

I think the whole point of critique (esp. in this particular case) is to provide feedback. In both my and the OP's mind, the shirt was created with at least some mild hope that people might buy it. Offering what I consider to be a valid suggestion on how to improve sales is not futile. Now, if the shirt was posted with absolutely no expectation of sales then I would agree with your point.