The relevance of the "social crusader" is an interesting debate, really.
Ultimately, I guess its just personal interpretation. How much you like the concept dictates how important you think it is. And there's enough "evidence" to support any position so you're at least a little bit viable no matter what.
And no, the creators weren't trying to make a political statement, they were two poor city kids just writing wish fulfillment. But their statements still had a political impact. "Wish fulfillment" is a pretty broad term and could have applied to any number of situations and topics. But they started with social, and therefore political, statements. And no, it didn't last more than what, a couple years or so (memory is rusty)? Its not even a blip on the radar of the character's overall history. Nor is it even his most successful era (that being parts of the Silver Age). Yet it's the approach that gave birth to a genre that has survived almost a century. And Superman is still going strong. So it had to have something going for it. You might even argue that its the most "pure" form of Superman; before he became a corporate entity (and corporate interference with the property is legendary from what I hear). And many of the greatest hits of comics (not just Superman, but the industry itself) are political (Watchmen, DKR, etc). You can point to the popularity of Morrison's opening Action arc, and DC's constant return to it over 5 years, as proof that the social crusader still works today. And you can point to Truth and say "no it doesnt."
Me, I adore the social crusader. It is, in my own mind, a critical part of Superman; part of his core DNA. And I think returning to that mentality (not wholesale, but spiritually) is possibly what Superman needs to re-connect with the audience and re-gain what he's lost. And I have my reasons, backed by several years of studying business (but not quite graduated yet so take that for what its worth), to show that I've got a point. But I know that this is just me justifying my opinion and wanting to see it implemented for personal gratification. The fact that it might actually work is almost happenstance.