Everyone, whether young or old, intelligent or not, should feel that they are contributing something of value
If the average person is not contributing at least the economic value they are consuming, your society is in a death spiral, and it doesn't matter how anyone "feels".
You're right about the economic value. I think that the best way to make someone feel valuable is to pay him for his services. A donation made out of pity does not evoke the same feeling of self-respect and usefulness in the recipient. It is also preferable that the payment should be made freely. I think affirmative action is debasing in this sense. If a black-old-female-gay-or-otherwise-disadvantaged person for instance suspects that the only reason he has his job is because the law required his employer to fill a quota, he won't feel as valuable as when he knows that his employer was under no coercion to hire him, but hired him simply because the employer thought him worth it.
So I think "feeling" captures the idea of economic value, and it captures the idea of an individual's happiness which is also important when discussing public policy.
Economic law always functions of course. Even under an affirmative-action quota system, a person is only hired if it makes economic sense as a whole to the employer. However, the employee may not feel as valuable.
With respect to topic, I think much of the angst felt by adolescents comes from them feeling not useful. Allowing them to be useful, i.e., to get a job and support themselves, would help them feel useful.
If someone's work is worth 100 units/time period but society spends 200 u/t to make them feel good about themselves, then that's a net loss. And this isn't just an academic point; a society that eats itself from inside like this can't last and will be replaced by something considerably less warm and fluffy.
You're assuming that by providing a "place in society" society is indeed trying to pull the wool over citizens' eyes. I think it's possible for a society to legitimately find good places for everybody to work without it being haberdashery. Just automate all of the pointless, frivolous tasks, and find more meaningful jobs for everybody.
The post I was replying to made the point that unskilled jobs should not be automated, but given to the "less able" to make them feel good about themselves.
If the average person is not contributing at least the economic value they are consuming, your society is in a death spiral, and it doesn't matter how anyone "feels".