The question of whether ageing is an illness has already been debated as of classical era, beginning with Terentius' assertion that "senectus ipsa est morbus" (ageing is an illness) as well as Cicero's centuries later argument in De Senectute that "pugnandum, tamquam contra morbum sic contra senectutem" (we have to consider ageing as an illness and fight against it).
These statements beautifully capture an age-old perspective on ageing as well as advanced age that has been tackled by several academics. Nonetheless, with the advent of contemporary medicine there in the 19th century, such an old notion had been pushed aside, because the primary focus was to define accurate medical phenomena (illnesses and symptoms) and their origins (infections, degenerative pathway, the genetics behind it, inflammation, etc.).
Perhaps the ancient people were correct, and ageing can indeed be postponed but even treated as an illness. The push to designate ageing as sickness has gained traction in recent years, not just among longevity advocates but also among scientists.
Labelling ageing as an illness, on the other hand, is indeed false and harmful. A natural mechanism becomes toxic when it is pathologized. So don't fear ageing rather take up habits that will help you in the long run. Understand what it truly means to have healthy ageing!!