Like it or not, the overwhelming majority of us do not actually want to live off-grid to the point that we are self-sufficient.
One of the basic principles in economics (comparative advantage) tells us to do what we're best at, then trade with others. In this way, we're both better off and get more of what we want. The great thing is that is is true even between a skilled or wealthy person and an unskilled or poor person. So, you're right, by not trying to be a jack-of-all trades, but through specializing and trade, people are better off.