You talk as though the incentive/agency problem was confined to the free market. If you want to see some real examples then take a look at government, religion, family, society etc. You can't change human nature, but you can create systems and rules to mitigate its worst aspects.
Depends how you make your money: honestly by free exchange, or dishonestly by force/fraud. Then there are the social benefits of (profitable) speculation to consider, although that's not why most people speculate.