Let's assume every claim in this article is true. Let's say that if you follow a certain diet, move to a certain island, make certain friends, and have certain genes, you will live to the age of 100. So what ? Best case, you get an extra decade or two of life. This may seem amazing, but to be honest, it's ineffectual life. This extra time will be spent being old . Whether you're 70 or 100, you will be frail, dim-witt…
Currently death is inevitable and a law of nature. Perhaps technology will change this in the future. As it is, it's one of the those things one must accept and come to terms with.
Perhaps you are a bit too depressed about aging. There are documented cases of peoples in their 70:s being quite keen and healthy.
I think one the keys here is exercise. People who do daily walks are much more healthy than people who don't. If one is in their 70:s and has been sedentary for most of his life and the other one has kept even a routine of daily walks, the other one has decades of exercise behind him.
There has been studies that moderate exercise helps to revert supposedly age related cognitive discrepancies. Sorry, can't find the reference right now.
My belief (anecdotal and completely unfound) is that people who live healthy lives are much more healthier when old. Thus part of the incapacity attached to old age is not biological predestination but also affected through the current and past lifestyle of the old person.
Sure, one CAN be in a really bad shape in their 70:s. Just sit decades on a sofa watching TV. Or perform work that is physically exhausting.
I think you are overthinking and fearing too much a thing you do not know thoroughly. That you refer to a scientific paper is an indication of trying to rationally cope with this. However, there is one problem - Most bleeding edge scientific studies are flawed and incorrect. I would not consult a single paper to form an opinion on anything. I would consult a gerontologist. And even his opinion might be formed from studying partial population - the sick and in need of care - in stead of the whole population.