Technically restaurants in real life is why we have fast food places too. But frankly for me - nothing beats going out to a real restaurant for a none fast food experience. You do not expect a restaurant meal to be in and out like Taco Bell or any of the fast food franchises. You expect a 4+ hour experience. My first job when I was in college was working evenings at a very nice, fancy restaurant - and the average table service was about 4-5 or more hours from start to finish for a table. Of course in a true restaurant meals are delivered in courses, one course at a time - allowing people to eat each course before the next part is delivered. We delivered 5 courses to each table - with a few tables ordering up to two more courses. It was not unusual in that restaurant to see the same folks there still at their table my entire shift. I worked from 5pm -11pm.
If you have never been to a full service restaurant - then yes you would think it takes a long time. To me it is pretty normal - as that is the dining experience I prefer. Maybe though this game could use some fast food restaurants where food is delivered all at once and fast- and save the fancy restaurant for sims who use them for a dinner date.