This is actually a picture of my apartment! Although I have a decent amount of light coming in from the kitchen, my living room actually doesn’t have any windows, plus my landlord picked a patchy beige shade as the wall color (and won’t let me paint over it, sigh), so I opted for an off-white rug to help brighten up the area. I used to have a dark navy rug and it made the whole space feel super heavy and essentially sucked all the light out of the room (sadly, I don’t have a “before” photo for comparison, but please take my word for it). The new rug made a whole world of difference and looks great against my gray couch.
You can also choose to paint the walls a brighter shade, but it’s a lot easier (and possibly cheaper) to add a rug to achieve the same effect.