What is the reason behing the mirror staying? It is reflecting railing, which is not interesting.

The books are too short, so I would remove. I would explore choices: 1) all white pieces on the mantel, so it's more cohesive. Right now, the thngs on each side do not relate. 2) if the mirror is hiding something and needs to stay, I would paint frame black or dark brown and change the mirror out for art. I would also change it to horizontal. Then bring more color with accessories. Be sure to vary heights on both sides.

Are those live plants on the coffee table? Try clustering them a bit more so they connect. Could do this on a woven/wicker tray to add texture. If not, put one on a book. What is the large piece on the bottom shelf? You could replace with a large basket underneath to keep throws nearby and to soften/add texture.

Just need to edit a little and vary heights. Put the books somewhere else, leaving the white vases. Cluster the coffee table plants on a tray and put one up on a small book for height.

Can the mirror frame be toned down a bit? Yes move the books. A large tray for the plants might group them up a bit better. I get the point of the blue vase on the mantle but it's not working.

Paint the white framed mirror. Edit and balance out the decorative objects.