I stated in my "Sources of the Economy" that marketing is essential to the economy. I partially agree, marketing can generate wealth indirectly by creating demand, but marketing only creates wealth when the end product is used for something functional.

If I market a music band, I create no wealth, I facilitate the exchange of wealth. I am not saying that this is bad, but I am saying that the creator is the basis on which everyone else operates.

I agree value can technically be created at the base level by controlling production of crops and things. You are right, but still this is dependent on the producer.

@bwarp you are right, engineers usually have clients and contracts for which they build.