If you take the emotion away from resuscitation, class it as any other treatment, and consider if we all have any right to demand anything from our medical teams?
Would you support someone demanding complicated knee surgery, that would not be effective and would likely damage the knee further rather than helping it?
While resuscitation is not considered appropriate for many patients, neither is a nose job or foot amputation. Surely the medics know the risks and benefits of offering any treatment and base their decisions on evidence. I hope so.
In this case, Down Syndrome is relevant to that person's history, but any person with advanced dementia and swallowing difficulties would be highly unlikely to survive resuscitation unscathed. Therefore resuscitation is rarely offered.
All of this should be discussed with patients, if possible, and next of kin as best practice.