I agree that the mantle itself is fine. You just have too much going on. The mirror is nice, but just not big enough. Don't put anything outside of the sconces.

[https://www.houzz.com/photos/modern-mediterranean-mediterranean-living-room-miami-phvw-vp~238645[(https://www.houzz.com/photos/modern-mediterranean-mediterranean-living-room-miami-phvw-vp~238645)

[https://www.houzz.com/photos/lake-residence-transitional-bedroom-phvw-vp~570768[(https://www.houzz.com/photos/lake-residence-transitional-bedroom-phvw-vp~570768)

[https://www.houzz.com/photos/new-canaan-private-residence-traditional-living-room-new-york-phvw-vp~2217578[(https://www.houzz.com/photos/new-canaan-private-residence-traditional-living-room-new-york-phvw-vp~2217578)

[https://www.houzz.com/photos/traditional-family-room-traditional-family-room-san-francisco-phvw-vp~154637[(https://www.houzz.com/photos/traditional-family-room-traditional-family-room-san-francisco-phvw-vp~154637)

On several of the photos there is trim on the mantle, Items are kept inside the trim and scones.

The mantle is lovely and you could tweek the accessoires..less, larger and consider a grouping of three which is visually appealing.

My Houzz: Feminine Chic Charms in a Chicago Rental · More Info

Your problem is one of scale. You have too many little things so that is why there is no impact there. I can't see the room to see what the overall style is, so I can only speak to what I can see. That mirror is too small for that stately fireplace/mantel. Put something bigger there. And remove all of those little knick knacks and put down a couple of bigger items.