"The problem is...it doesn't work...does it? The voters always get the choice between Big- money-backed-governement1 and Big-money-backed-government2. The money is the same money..."
Well, for the time being this is above all a US problem. For the last 2-3 decades only a minority (less than 50%) of the population voted in the US and nobody took action, while that was a clear sign democracy was not working.
Not to take action is a choice you made and you will have to bear the effects. It does not surprise me that a 2-party system gets corrupted, like the 1-party systems in Russia or China.
Time to change. Please, start fighting for a change.