This seems like a shallow take on a complex subject.
It seems overly simplistic to unilaterally claim that our brains decline past age 30.
Sure, under some metrics. Under others they improve [1].
There's a reason why we don't put 20 year olds in charge of our nuclear arsenal, for example - and it has nothing to do with the ability to remember a sequence of 7 numbers instead of 6.
[1]https://www.health.harvard.edu/mind-and-mood/why-you-should-...
