Tips for Better dining experience In Sims 4:
1) A little preparation before you go.
2) Make sure your Sims needs are in the green.
3) Have the kitchen on the same floor as dinning.
4) 3 waiter station, two Hosts, and at lease 2 Chefs.
5) As soon as you get to the table order your main course and drink.
6) As you get your first order to your table, order your second course or deserts.
7) Your table must be clear to be served, if not clear let your sims clear it.
8) Do not add dining tables to a second floor or outside that will slow down the waiters.
Any place its a table and a chair on the lot, it will be included to be served.
**Seems to me they have speeded up Sims eating in restaurants.**