Maybe it should not be limited to doing one thing really well but certainly some restaurants where I live/grew up are focusing on a very narrow food menu.
Take for instance Johnnie's Beef in Arlington Heights and Elmwood Park, IL. They limit their menu items to almost only Italian Beef's and Italian Sausage. They are super fast and the food is very good. When I ate there today I was amazed at how fast people walked in and walked out with their food. And this was during peak lunch hour. I was originally worried there would be a huge line. The focused menu allows them to streamline and optimize everything very easily.
Could you narrow your product offerings to your top 20% of items. Can you really justify your wide selection of products or products that don't add value to your business? Can you improve your inventory or speed up your shipping or preparation time with a more focused offering?
Don't be afraid to focus on profit and reduce items that don't sell.
Photo Credit: Johnnie's Beef Facebook Page