I would remove the brown granite rather than paint it or try to hide it with a large mantel. It covers such a large area that painting it may still leave the fireplace looking heavy and dated. Since the original red brick is still underneath, I would ask a fireplace mason to remove the granite carefully and determine whether the brick can be restored.

If the brick is in reasonable condition, I would clean and repair it, then add a fairly thick wooden mantel in a color that works with the brick and the rest of the room. The mantel should be properly installed at the required safe distance from the wood-burning insert.

It would be helpful to see photographs of the entire room, not only the fireplace. The best brick finish and wood tone will depend on the flooring, furniture, wall colors, and the overall style you want to create. The position of the TV also needs to be considered before choosing the height and depth of the mantel.

The reason the rest of the room matters so much is that the same fireplace can look completely different depending on the colors, lighting, materials, furniture, and decor around it. I explored exactly this in a design video where I transformed the same living room in four different ways while keeping a fireplace in every version. Seeing the four complete interiors may help you decide which direction would suit your room before choosing the final brick finish and mantel color:

https://youtu.be/R-2ZyyBc6EY