I'm pretty sure it's fireblight unfortunately. My tree looks the same way.
From what I've seen, it usually affects the younger branches most on a healthy tree, but it can spread to the older branches also. I have seen it infect branches that were a few years old on my pear tree, and sadly it ruined a whole crop of pears this year.
I'm trying to decide what to do with my apple tree, whether I want to try to keep it and see what happens, or go ahead and replace it. I have some baby apple
trees, so I will probably just replace the Granny Smith with one of them, since fireblight gets even worse when the tree starts flowering, as the flowers are a prime site for the infection to enter and spread.
My pear tree that did lose the crop this year has made a good sized crop before, so it
should be possible for the tree to produce a crop, just maybe not reliably, depending on weather conditions, bloom time, and other factors that may affect the severity of the fireblight.
Some natural ways that may help the tree fight it off, if you decide to keep the tree, include making sure that the soil it grows in drains easily and is not waterlogged, and creating soil that is full of organic matter from mulching with leaves, branches, logs, and other plant debris, which can help provide the right nutrients and encourage beneficial fungi that will greatly help the tree's immune system!
Hope this helps a little and hope your tree recovers quickly and thrives for many years!