Shoulder work falls apart when the stretch is either too aggressive or too vague. A strap makes the angle adjustable so you can move the joint without turning every rep into a shrug or a wince.
That is why it ends up being one of the cheapest tools with the longest shelf life.
Use the strap well
The point is cleaner motion, not forcing range.
- Keep tension light enough that the shoulder stays relaxed while the arm moves.
- Pause in the ranges that usually feel sticky, not just the easiest part of the path.
- Pair strap work with a roller or posture opener if your upper back is the real limiter.