is my old apple tree dying
Over the past two years, my 25-year-old apple tree has produced limited amounts of apples. Also, the leaves are reduced by 40%... the bark is splitting, peeling and falling off. At this moment, you would think it was autumn; the leaves are dying and ready to fall.
Your tree definitely looks in bad shape. 25 years in not at all old for an apple tree, unless it's maybe a dwarf variety. I can't tell what's wrong by just looking at a picture, but I would guess the problem has been going on for at least several years. You would need to have a certified arborist come in to look at the tree; I don't know whether you can save it at this point or not. This article might give you some ideas of what you're facing: https://www.gardeningknowhow.com/edible/fruits/apples/apple-tree-diseases.htm