Age does bring wisdom, at least for most. They look back at the stupid things they did in their twenties, and see twenty year olds doing the same as they did. Youth is wasted on the young.

Saying that youth are stupid and old are wise is nearsighted. Both play important roles. I would never ever voluntarily confine myself to a society where everyone is wise and no one does stupid things. Nor would I want that for my kids.

Yes both have important roles. The older you are the more experienced you are, while I expect societies would stagnate without the young. However I would myself like to be in a society where everyone was wise and didn’t do stupid, meaning harmful, things.

I'd give anything to be 14 again.

> there is in fact a procedure that allows to reset BOTH the body and the mind into a clean healthy state. It's called "having kids".

You must have not met many parents because this procedure you speak of isn't guaranteed at all to do this reset you speak of. One could even argue that this outcome is the outlier. Go work as a teacher at a secondary school and tell us the percentage of parents whose mind and body is in a "clean healthy state".

> Even if at 90 I had a body of a 20 year old, I would still have the mind of 90 year old. With all the experience, all the mistakes and presuppositions and biases.

I think you're underestimating how many of your thoughts, inclinations, moods and attitude are driven by the body (hormones, energy, etc). The mind is not separate from the body, they are one system. If you rejuvenate the body, the mind is also changed. I agree neuroplasticity is something that needs care as well, but it's simply not the case that it's a separate thing.