I think you are the one being a twat. Everyone's IQ and ability to grasp new things falls with age, but falls at very different rates, and from different starting points. Most people struggle while still at high school. Some people grasp most new things with little effort when they are 90. The problem is not age. Its people who started out with the short straw in life, and will NEVER grasp anything moderately complex without massive reinforcement. Modern society really has no place where they can thrive.
So what is the logical consequence of that statement?
Logan's Run?
Huh? Are you having a problem grasping concepts, either here or while reading/watching Logan's Run? Something like 9% or 10% of the population are of such low ability, even when young, that people with a wide variety of needs, like, famously, the US Army cannot find even simple tasks for them where their presence is a net positive. If we make simple base line tasks, like making simple payments, more intellectually challenging you can rapidly exclude way beyond that 9 or 10%, even among the young and physically fit. It just gets somewhat worse when looking at an older cohort. Combine this with failing education systems graduating more and more people who presumably follow typical norms of ability, but who have been taught very little, and an ever more complex baseline for living could be a true catastrophe.
If you didn't grasp Logan's Run you had a cohort of very similar ability people. Not too bright. not too dumb. Poorly educated with a web of lies. All reaching a similar level of degradation at the age of 30, and all being bumped off in a public spectacle they'd been left too dumb to grasp.