LMSC I disagree… In a small independent that doesn’t care about the coffee, in the management, choice of beans or training of staff, I agree there is no point. Its like complaining that McDonalds doesn’t produce a high end burger for you.
However in proper speciality shops, it might just be that the barista had an off moment, and misjudged the shot, or was so busy they hadn’t realised they needed to adjust the grind for instance. In those cases pointing out the poor shot can (hopefully) get you a good one made without any complaint.
Of course if its your first time in a shop, its hard to tell whether what you got was as good as they can do, or as good as they want to do (or are bothered to do).