I wish the concept of a milk bar would spread to America from Central/Eastern Europe. They are essentially a mix of an American diner and a cafeteria, where you can get cheap, good food that is already cooked (with a few exceptions like pierogi.) Think Chipotle but with local specialities and with an 80s communist-era vibe. It is usually fast but is much healthier than typical fast food chains.
Milk bars were started during the communist era and are still popular amongst the older (70+) crowd, but modern versions are a go-to for younger people too. And so you'll usually get a very interesting mix of society sitting side-by-side. Not quite a family dinner restaurant, but is a social restaurant concept nonetheless.