Perhaps naive but from NPR this morning: "For people who live with chronic pain, getting up, out and moving can seem daunting. Some fear that physical activity will make their pain worse. But in fact, researchers find the opposite is true: The right kind of exercise can help reduce pain." https://www.npr.org/sections/health-shots/2019/09/23/7548691...
But absolutely not for all conditions. For too long, doctors have pushed graded exercise programs for essentially all chronic pain conditions, despite good evidence that it can be harmful, even permanently, for some conditions (e.g. CFS).
I personally suffer from chronic pain, caused by small fiber neuropathy. I used to love walking, and I want to exercise - but if I do too much it can take days or even weeks to recover. A few times, I'm fairly sure I made things permanently (or hopefully semi-permanently) worse.
So, yes, exercise does help some people, but we must be careful not to push it as the be all and end all.