"They made us wait, but there were empty tables!"
Yes, because those tables were booked by people who bothered to make reservations.
"I saw other people get their food before us, when they had come in after us!"
The law of physics says that some items take less time to cook than others. If you are looking at your watch while waiting for food, or indeed watching how other people get served, you are not here to enjoy your meal.
"The waitress was surly!"
Yup, good complaint. No reason for that.
Except that hospo workers are people too. Maybe sometimes you forget that.