I think "efficiency" is not the right word when were talking about things on that level. Efficiency in a marketplace, I don't know, maybe. Efficiency in getting the goods people want where they want them (despite sometimes also getting the goods people don't want where people still don't want them). Capitalism is efficient for consumers. If you want something there are probably 10 or 100 or 1000 people trying to get it onto your hands right now.
A low efficiency restaurant can stay in business if they have the sales to cover it. I mean there are dozens of workable business models for restaurants. You can stack 'em deep and sell 'em cheap, or you can be exclusive and have 10x the average tab per customer, or you can manage your inventory perfectly and have average traffic and average prices. I mean there's a lot of ways to run a restaurant. Yet, most restaurants go out of business within a year or two of opening.
Capitalism keeps restaurants around because they are the ones consumers prefer. That's the primary factor. If people want to eat there and you're not being stupid about your inventory or your labor costs or your waste, you'll probably be able to figure out how to make it work. It's only once people decide they don't want to eat there that you have to become dedicated to efficiency in order to hold on just a little bit longer.