There are good and bad elderly drivers and good and bad young drivers.
This is not good vs bad, but different phenomenons. No one sensible disputes that younger drivers have more accidents, generally caused by inexperience and overconfidence. This has been tackled by a series of measures like making the driving test progressively more rigorous, a theory element, a 2 year probationary period and with motorbikes a series of restrictions on what types of bike new riders can access. Licences issued adter 1997 also restrict newer drivers abilities to tow heavy caravans or drive minibuses.
Eventually most of this cohort will improve, learn they aren't indestructible etc and gain experience. They will be far better drivers, in most cases by thr time they are 27, compared to 17. For this group thr problem is behavioural rather than a physical or mental decline.
The reverse is almost certainly true of an 87 year old let alone a 97 year old. As we age, we suffer slow irreversible physical and mental decline at which point we shouldn't be allowed to operate a two tonne killing machine. The cut off point will come sooner for some than others, but it is striking that whilst we have ever stricter legislation impacting on yoinger drivers (and a good thing it is too) older dangerous drivers whose poor driving is caised by irreversible decline are effectively left to police themselves. In my view post 70 you should have to submit to regular medical tests when your licence comes up for renewal (every 3 years) and with an absolute cut off point of 85 when you surrender your licence. I'm sure there will be many citing grandparents who are still competent drivers, but equally there may well be people who are mature enough to learn to drive at 15, but an age lomot of 17 is in place for sound reasons. A line has to be drawn somewhere.