Robert Alfons has a point.
By American standards, Obama is left, Bush Jr is right, Clinton is left, Bush Sr is right, Reagan is right, etc. However, wealth concentration by the less-than-1% has risen, money has increased its influence in politics, worker protections have diminished, constitutional rights have been weakened, etc. The policies of Obama and Bush Jr, or Clinton and Bush Sr, diverge on social issues, which are largely a symptom (e.g., dependent on) of the greater problems. As a result, a claim such as "Obama's and Bush Jr's policies are only marginally different" is considered ridiculous, when in truth, both are incredibly similar.
The range of ideas is very limited in American political discourse and this enables the continued benefaction of a very small portion of the population. Refraining from looking at the greater scope of ideas, and examining our politicians within said greater scope, is not beneficial; it's backwards. You're essentially arguing about a handful shades of a couple colors, when there are hundreds of shades and thousands of colors beyond that.
I'm an American, and I agree at looking at the demands we have for our government through the lens of a broader background of ideas and possible solutions. Frankly, while his ideals may be even more progressive/social, Bernie's proposals are only a little left of Obama. (But then, I think even Obama wants to be left of Obama)
But I personally see that as the sweet spot in terms of economics-- where you have a price-setting market that manages the efficient allocation of most goods and services and drives economic growth, but has practical regulations/oversight that ensure high competition, a relatively level playing field, consumer protections, and enough transparency for businesses and individuals to make better decisions. Also, make-sense government control over industries that don't perform well as a free market (some utilities, arguably health), and subsidizing of important initiatives that don't make sense for-profit (see: subsidizing antibiotic development research, where you want to make something that we will use as little as possible). Also social services that maintain a broad level of standard of living and redistribute a certain degree of wealth-- which ultimately also benefits business by helping to maintain a healthy/growing market. While I'd say this is the general advocated vision of everyone we would call anything between "moderate liberal" and "social democrat" here in the US, the actual dedication towards that vision seems to vary...
Maybe it's because I'm American, but I see that sweet spot as the ideal, though it is quite conservative still on the world stage. Actually, this is quite close to the reality of Japan; though a poor worker's culture, comparatively weak innovation (to the US), and greater social conservatism are issues.
Anyway, a true and updated glass steagle, regulation over dollars spent in politics/lobbying (ie. fix citizens united +), and improved systems of health and education support are the key pieces needed to hit the sweet spot-- you know, just the things that are exactly the key pieces of Bernie's campaign; though it's not like Obama hasn't also fought the good fight.
Overall, I'd say that people are right in saying that we're fighting over a very small range of ideas when looking at Hillary, Obama, Bernie-- but somewhere in there is the sweet spot imo. Human corruption/greed and lobbying, wayyy too much call for abolishing a "big brother" that isn't there, and other factors have left us with an economy that is starving and not serving the majority of our citizens, but that doesn't mean the vision is wrong-- but it definitely isn't realized.