The designer was trying to make the fireplace visible from everywhere. Perhaps you could put a couple of comfy armchairs right in front, and then rearrange the rest of the furniture as if the fireplace isn't there. So, you would have a little conversation area just in front of the fireplace, and then a TV/hangout space in the rest of the living area.

Unfortunately this doesn't work as the seats would block the way through to the dining area.

Wall of bookcases or giant mural on blank wall. Your sofa placement looks brilliant.

Unfortunately I can't read the measurements on the floorplan.
So, had to guestimate, but would this work? So you can walk around the sectional?
With the TV on the wall with the window, where the tall plant now is. I'm thinking of using that media cabinet that you have now, take it all the way to the corner, but maybe have a taller cabinet in that corner. If there's enough space you could have a row of bookcases (the height of the back of your sectional) along one side of the sectional, or a long sofa table with lamps on it. But it's fine without if there's not enough space for that. An arc lamp will give you light too.
Think big canvas art, a striking wallpaper or a colour on one or more walls.