I don't disagree. But between experience, resources amassed, and relationships built by the time you turn 40, it's often possible to have a greater actual capability despite your slightly reduced theoretical capability.

Basically when you're in your 20s you might have a bit more cognitive horsepower, but you typically lack some emotional and financial tools to leverage that horsepower more efficiently.

I genuinely don't get how people delude themselves into thinking aging is perfectly fine, we've always known it's a terrible process and we've sought to defeat it for thousands of years. It's also wild to me that we aren't putting a truly stupid amount of money towards that goal either, emperors used to understand that finding the cure to it was worth literally everything. Yet here we finally are with the ability to meaningfully and exponentially progress our knowledge and we aren't devoting our entire society to it.