What's the point of living to your geriatric years even if your mind if sharp as can be, but your body has stopped being functional?

None.

The idea of continuing "until a fix is found" is simple dreaming and torture.

The alleged need for a "Quality of Life", demands Mercy for those who want it.

Because ideas stimulate purposeful activity.  Without the idea, activity is pointless.

Einstein, Newton, Locke, Hume, Pythagoras, etc. changed our world with their ideas.  No one records their  pole-vaulting records.  Besides, merely because an old dog can't chase cars anymore doesn't stop him from nibbling on the tires if they're parked. 

I see we have at least one REALLY STUPID F in the audience.    

It's preferable to death (most of the time) 

You could ask the same thing about babies and children. They are even more useless than old people.

The point is to live life to the fullest, which is what most of us geriatrics do. 

A better question - what's the point of living life with such a negative and limiting outlook?