Out of curiosity, I looked up the definition of illness. Seems to be so loosely defined that it can be either a disease or a patient's personal experience, including "lethargy, depression, loss of appetite, sleepiness, hyperalgesia, and inability to concentrate", which (possibly excluding hyperalgesia, I've not heard of that before now) are associated with aging.
Regardless of if "illness" is or is not a terminological inexactitude, it looks like ageing is a chronic progressive terminal genetic disorder. I think "cure" is an appropriate term in this case.
Involuntary ageing is the very worst tragedy of human life.
Funny that this kind of ideological conflict will likely be a key fulcrum of the machine intelligence revolution. We will have a very loud minority that attempts to forcefully prevent all other humans from having the voluntary choice to avoid suffering.
Imagine a list of things many people wish to happen in physical reality. We’ll have more of that.
-Better healthcare
-Curing most things that destroy quality of life
-Curing aging and age-related death
-Much better treatment for all sources of mental suffering
-Far better and cheaper and reversible body modification
-More free time to spend at whatever you want
-Everything much cheaper
-Bigger and better homes and living spaces
-Bigger, faster, cheaper transport
-Easier to organize meaningful social interaction
-Better and more immersive entertainment
-More time to spend with close friends and loved ones