With due respect to Scott and Mamuang, I’d like to differ at least a bit. Partly this is based on our own trees, many of which are five or six years old and have yet to be sprayed. The leaves do look a little raggedy by the end of the growing season, but I’d call them closer to mostly ok than really sickly. They have also started to produce fruit, most of which has been sound when I’ve been able to beat the squirrels and birds to it. That being said, I concede that it’s early days yet for our trees and things could certainly change.
What I find more persuasive, at least for myself, is the entirely untended apple trees that I see around where we live. Like our own trees, they may look a little ragged as things wind down, but they seem to be healthy enough overall. Some of them have pretty clearly been growing for decades, and some of them bear a good amount of fruit that I’ve found to be sound in spite of the tree being left completely to its own devices.
I wrote about one such tree a few years back in this post: Which apples do you have ripening now? - #78 by JinMA