First, If we would never try what in the past has failed then we would be really in a very stagnant state. Second, the EU has not failed, the EU is still the main reason for the prosperity most of its members have gained and still continue to gain after WWII. That it has had some backlashes recently does not mean at all that it has failed.
> The EU is not necessary for free trade.
It is not. It is however necessary for a internal economic market that guarantees the free flow of capital and labor, which is much wider/different in scope than free trade. Free trade can be arranged with a few trade treaties in neo liberal style.