I am pretty shy but I will always tell the chef or the waiter or the manager if the food did not live up to my expectations.
I figure nobody who cannot cook should ever be a professional chef and it you have no idea about food, another profession might be a good idea.
It never ceases to amaze me how many people have the gall to charge you money for what amounts to not even bad home cooking.
I also always leave reviews on various sites and will tell friends and family not to go there as well.
As far as I'm concerned a restaurant is a place where professional chefs and staff work so I feel no need to stay quiet and taking bad food or bad service.
You can be polite but still frank and honest about your experience and feelings.
There is no excuse for a bad meal in a restaurant.
I don't know enough about the law to open a law firm, why should someone feel arrogant enough to think they can cook in a professional kitchen when they have no aptitude for gastronomy ?
It seems quite reasonable to expect a minimum of standards when you go out to dinner !