I dont think thats not fair at all. Yeah Feige is the coach, but the Russos were his 2 superstar best players. They fit Feiges system perfectly, but they proved to be fantastic action filmmakers and deserve all the praise they get.
Its not crazy to wonder if things will be quite the same without them.
Its quality control is what people are concerned about. Not how much these films gross or glossy special effects. Why do people have a hard time separating quality films from highly grossing films? They come together occasionally (like the Russo Bros films), but there are a lot of dudes that made a lot of money.