Marvel’s Luke Cage has superhuman strength and bulletproof, unbreakable skin, and that’s way too overpowered to be a “street-level” hero. What makes characters like Spider-Man and Daredevil “fun” is the fact that they are vigilantes who can be hurt; they can be shot or stabbed, and their friends worry about them because they aren’t indestructible. But when you have a character that’s indestructible, then all that danger goes away. Also normal thugs aren’t a threat to you.
The reason he is a street level hero is because I believe he was created for that. It was important back then (and still today) to have a bulletproof black man in comics. Luke Cage was the first African American Marvel super hero to get his own comic (Black Panther being the first over black Marvel hero)