I know how you feel - my step mother (who passed away) got alheizmers and was absolutely furious when the Doc confirmed she could no longer drive as she did not recognize the symptons, but it had to be done.
Older age inevitably leads, or can lead, to slower reactions, poorer eyesight/hearing/senses but when it does that can vary so much from one person to another. It is also obvious that come retirement car choice is usually restricted due to price/running costs and inevitably leads to smaller and dare I say more basic cars that means their pace on the roads and making manoeuvres is often frustrating and can even be frightening, as the examples above reveal.
Tolerance of other road users, even learner drivers, can often seem questionable and that creates an "us and them" that can lead to bad driving through frustration. But we also need to remember car insurance premiums reflect the inexperience factor for new drivers or known risks and oldies will get their premiums hiked in the same way as their health and travel insurances, until it is no longer viable.
But as hard as it is, yes it often does mean close family members are the ones who normally have to say when they should stop driving and I am dreading the day that happens to me. And that is going to happen to everyone else on here at some point in time, so enjoy your driving while you can.