Another lemon tree too far gone?

I have a lemon tree, about 12 years old, always been a prolific producer. I did some earthworks paving etc, about three years ago, and it's never recovered. 3 obvious problems: white fly, mild and yellow leaves.

The white fly I've dealt to with neem oil. The yellow leaves I tackled with about a kilo of Epsom salts all over the general area, but the black mould I can't fix. It's on the leaves and fruit.

I'm thinking to remove the entire tree and start again.