It looks like it could be cedar
apple rust, a fungus. Do you have cedars or junipers nearby? They can be anywhere within 4 miles, but if they are within hundreds of feet, it is quite likely. A bad infection makes the fruits commercially valueless, but a few spots on the leaves is ok. It doesn't harm the fruits if you use them right away, and the
trees can live on and on. The worst of it is cosmetic.
The best medicine is cutting down every cedar and juniper in a 4 mile radius... Also, mulching well, good soil health, the usual. THere are apple cultivars that are more resistant.
I have it here, and most of our apples go for cider but we do have some good ones. Look up images of "gelatinous spore horns of cedar apple rust galls" I have them on a cedar right now. THey are otherworldly.