Gene Roddenberry’s ideology, which was that humanity would go to the stars having overcome the colonial impulse, has clearly failed to take root in the popular culture.
I don't think the problem was that space mania didn't take root in popular culture; space mania was pretty big in the 60s and 70s. But it was big only in a superficial, decorative sense. What failed to take root was something deeper — a sense that this was something we all could (and ought to) take part in, a sense of the mission being shared amongst all of us equally instead of just being reserved for a select few heroes.
Cosmos and the rest of Sagan's Soldiers tried valiantly to show that science and space exploration weren't just something for the chosen few, but things all of us could, can, and should do. They're still trying, and some of the blood has started pumping back through the veins of that nearly-lifeless body (Mars missions, crowdsourced space travel, etc.), but it's still rough sledding.
Patrick Farley, a fellow Gen-Xer, created a webcomic — among my very favorites ever made — called The Guy I Almost Was,that touched in part on this problem. His protagonist believed, naïvely, that he wouldn't have to do anything to inhabit a great future of space travel and flying cars and a workless, automated economy. Rather, it was already being hatched in the laboratories of benevolent corporations (are you snickering yet?), and all he had to do was stick around long enough to inhabit that future. Then he grew up and found out "the future" didn't much care for him, that "the future" was largely a fiction created by people out to sell something, and he cast himself in the role of an atavist. Then the Internet came along and ruined all that for him, but not before he had a chance to understand the value of not being seduced too easily by a vision — whether of the future or the past.
This business of "be the change you want to see in the world" is so easily reduced to the level of cliché — and, from what I've seen, also so easily used for ill as well as good. (What if the change you want to see in the world is destructive and malign? How do you even know it is?) But being the change is necessary, because without it nothing happens at all.