What is wrong with my poor Apple tree?

[Isthismynamenow]

And what should I do to remedy it?

Mine is the same. I think it's aphid damage. They suck the moisture from the leaves and then sunshine scorches them. The fruit are also damaged by rosy apple aphids. My poor apple tree has been like this for the past three years, but particularly bad this year. I tried removing aphids by hand (ie squishing them) this year but I think next year I'm going to have to use a spray of some kind.

Could be blight. When was the last time it was pruned?

It looks like a result of the dry weather we had May/June. It has caused bitter pit in the fruit which is a calcium deficiency that is brought on by a lack of water. The leaf scorch is less definitive but if it was dry enough to cause bitter pit then it would’ve been dry enough to affect the leaves. https://www.rhs.org.uk/problems/bitter-pit-in-apples

It was pruned last year. There’s been a problem with the fruit for a few years now, with hardly any healthy ones, but the issue with the leaves is new this year.

Depending on where you are, you might have a local community orchard? I'd suggest getting in touch with them and having someone out to investigate/bore you to tears.

I jest, they're always very helpful and knowledgeable.