It really isn't. Mainstream Democrats like Pelosi and Schumer actively work against the more radical Democrats (sabotaging Bernie in the last primary) and are into big business and banking nearly as much as Republicans are. That's why the Democratic Socialists of America exist -- right now as a group within the Democratic Party, but conceivably as their own party in the future.
Putting aside the fact that Bernie isn't a democrat...
Most of those in government (just to make abundantly clear I mean both parties here) are there because they want power and money, not because they have principles.
