I don't see that the left has a concept of what we want as an alternative economic and political system

This is hardly unprecedented. There was broad agreement on many of the problems in France in the 1780s, but no broad agreement on the solutions. That did not prevent there being significant beneficial accomplishments from the revolution, along with the notable horrors.

But I do agree that an alternative vision that could gather broad support would be very valuable. Perhaps a continuing effort to widen the understanding of the problems inherent in the current system along with the bogus basis for its widespread support is a necessary first phase. What are needed are nonviolent but effective ways to discredit the dominant view disrupt the standard narrative. When politicians are hissed, booed and reviled for spinning the same old lies and narratives we will know progress towards a new social organization is happening.

It is becoming harder and harder for TPTB to maintain the pretense that everything is under control and operating according to legal and constitutional norms. The more people who publicly call out politicians and regulators by characterizing what they are doing as being front men for criminals the better. Well over 90% of the population of most formerly 'first world' nations are the victims of this collusion. When a substantial majority of the citizens realize this we will be closer to effecting some change.  

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."