As others have said, it’s just a standard form letter to the effect of “deal with it yourself as best you can; it’s not something we want to be involved in” which really makes sense, since the gym did provide you access to the equipment.
This is really no different than if you were to sue them for not having a stationary bike you could use. Could they provide a stationary bike designed for upper body use rather than leg use? Yes, they could. Is it reasonable to expect them to do so? No, it is not. It’s the reasonableness that you need to consider here.