About 50% of what I order at restaurants I change something. If I need to change more than one thing I usually don’t order it, because I try not to torture the waiters and kitchen staff. Unless you count hamburger with double lettuce and nothing more as changing more than one thing because a burger is typically served with lettuce, tomato, and onion. Sometimes there are no hamburgers on a menu just cheeseburgers, so hold the cheese another change.
I don’t order a lot of burgers though. Typical changes are more like sauce on the side, or no sauce, or rice instead of mashed potato.
Another change I often make is no parmesan at Italian restaurants.
Chinese I often get plain white rice if the combo comes with fried rice, or white rice in lieu of pancakes for moo shu.
Pizza I usually order plain, but sometimes I add mushrooms or sausage.