I’m not sure what you don’t like with the example render. Shooting with a real-world camera straight at a bright window is often difficult.
For realistic lighting of a room, I usually set up a Corona sky and sun, finding a good angle for the sun. If I’m after a particular look, I replace the sky/sun with an HDR. Then, it’s a matter of balancing the outdoor light intensity with the camera’s exposure settings, just as you would when taking a photograph indoors.
Adding glossiness maps to the various surfaces also increases realism. And an outdoor ground object and some simple boxes (to mimic surrounding buildings) make light bounce correctly from outside the windows.
If I’m not happy with the results at that point, I add more or larger windows, perhaps a skylight (ie. let in light through a few spots in the ceiling), a few non-natural light sources and probably a bit of haze. As a last resort, I would render the room in two different exposures - one to get the window right, the other for the interior.