It's easy to be cynical, and to sneer at exuberance and deride it as irrational.
We don't have flying cars, but we have something better. We don't have moon bases yet, but we have developed the means access to space at 100th the cost. Our robotic butlers are extant, if ethereal in the Cloud.
Even ten years ago it would have been conceivable to write such developments off as infeasible. If the engineers behind such great chains of innovation had abandoned the hope of accomplishing these feats, we would be robbed of them.