Many people on this site are fond of Romabio, a product produced especially for brick. It appears to be much better than regular painted brick which always looks thick and gummy to me.

You didn’t mention the copper or brass trimmed firescreen but I assume that’s being replaced.

I like your brick, just the way it is. What I dont like, is that because of the wall itself having the brick on it, and the one on the other side of the fireplace, not having it, the whole thing looks top heavy on one side. I would either add the same brick (if you can even find it anymore), or remove the brick, from the wall on the other side. I would remove the shelving too on that side, and make both sides look alike. If you like and need shelving, then have new shelves built for both sides, so they match. I agree, the mantle needs to go. The existing, isnt quite the right size, and it is also a wood color, that does not go well with the brick. I see no reason for the hearth to go all the way to the wall either, so I would want that to just be the length of the fireplace.

Drywall the fireplace; upgrade the shelving; paint the brick wall; add a low console for a t v . Definitely....change that fireplace screen.

I like the brick also. Agree with @cat_ky about getting of or drywalling over the brick on the right, cutting the hearth so it is just the width of the FP wall and getting a new mantle. I would not like it to be modernized as picture above.