Although I think it’s always kind to be polite and constructive with feedback, I totally disagree that you have to be as capable a cook as the chef to critique their food.

You don’t have to be a culinary wizard to tell when many foods are overcooked, underseasoned, etc. Sometimes chefs just screw up and a dish has outright unpleasant qualities.

Most people have hundreds or thousands of points of comparison for high-quality food even if they can’t make it themselves. If a restaurant bills itself as high-quality and then doesn’t live up to that standard I think it’s perfectly reasonable to say so.

Is peer review more valuable? Probably. But most restaurant guests aren’t chefs so pleasing non-chefs is valuable too.