Gee if only your photos really illustrated the total room!!

Can you add any pics of rooms you like? that will help folks give some direction

Remove the surround. Find a local artisan to create a mantle.

IMO the fireplace surround is quite handsome, certainly NOT builder's spec. I would keep it

Based on the stairrail, the style is meant to be modern, so the surround should be fairly minimal, as it is. So I don't think there's anything wrong with it. Once the room is furnished and the TV is over it it will look different. You could get a frame TV to make that look better.

Yes, it is modern. Were you wanting to turn this modern space into a rustic one? Why a mantle? Google modern rustic ski chalet and see how this could work beautifully in your space. I would urge you to place your tv elsewhere and leave the space above the mantle for art. The other walls, please???

I would keep the fireplace surround as is, the style fits with the surroundings and will look quite nice once the room is furnished.