You can paint/stain it or apply porcelain or stone over it.

You could have plaster or microconcrete applied over it.

I'm sorry you don't like it. It looks like a fantastic example of MCM. If you can't live with it, I would build a frame over it and apply a different surface material so someone could remove it in the future and get back to the original.

What does it look like without all the decorative items? The niches could use some discreet lighting for artistic sculpture or vase. Instead of mirror, art over the mantel and a vase with arrangement that reflects style and colors of art and art pieces. Another observation - what is the function of the space between the etagere’s? Maybe addressing this area will rebalance your fireplace visage.

I think the fireplace brick is the best part of the room. For me what isn't working is the color of flooring and mismatched furniture. Also as above, ditch the mirror and do dads on fireplace as well as the small shelving units.

Agreed, the fireplace has got to be changed. That is not an example of MCM that needs to be preserved. Do you use it as a fireplace still?

The whole architecture of the room is awesome! I agree with kandrewspa to frame out over the fireplace if you absolutely can’t live with it. It would be heartbreaking for it to be removed or painted/tiled over. (Also hoping you never paint your ceiling and window frames!) The room has great bones. Lean into a modern take on the MCM even more for a cohesive look.

Before doing anything to the fireplace, I would replace the decor on the fireplace and walls for more impact (ex. family photos above piano, black pendant (hung lower), large ceramic vases in niches, large colourful canvas on the mantel, black tray on the coffee table, contrasting accent pillows).

This might be too drastic put painting the wood wall white or off-white would help enhance the fireplace. Love your house!

Your room has a bit of character and in a good way. The wall to wall carpet needs to go.

Not MCM but interesting but to me the stuff all around it to hide it just makes it worse this skinny shelf things , all the mantel decor with no real reason , the lonely white out of scale chair lots that can be fixed before touching the FP How about a long narrow tpestry type piece to cover both empty spaces on the left a minimal decor on the mantel not a mirror and then see how it looks paint the brass black, get some nice flooring done not carpet then see what the room looks like . Furniture scale is an issue that brown chair one big thing the little white one all wrong and the blue sofa is nice .