--- NASA and human exploration of space in general reminds me a bit of an aspiring polyglot who has still failed to learn a single language to fluency. Our lack of focus on a single area plus small budget has left us stranded on Earth. Focusing or largely focusing on one area, on the other hand, is the opposite: upon learning a language to fluency it reaches a kind of self-propelled status where it becomes a part of you, something that only takes a slight bit of effort to maintain. Mid-level fluency is the opposite: while somewhat useful and kind of fun, maintenance is harder and the language remains a useful skill only in certain limited situations.
* Concentrating on space station design could have led to a small Stanford Torus-like city (okay, settlement) with partial gravity (0.1g for example), complete with greenery and water and the like, and the more people that live there the more of a character of its own it would develop. A destination that is interesting in and of itself would attract much more tourism and aspiring settlers than the ISS, which is a floating lab from which one can look at Earth.
* Concentrating on telescopes may have already led to the discovery and simple imaging of a very, very earth-like planet nearby.
* Concentrating on the moon would have led to...people living on the moon. Similar to the station above, the settlement may have developed a quality of its own that made it attractive as a place to live, do research, and work.
* Concentrating on propulsion may have led to cheaper access to space, the largest barrier to becoming a spacefaring species.
A much larger budget, of course, would easily result in one or more of these situations. But in the meantime humanity exploring space is a bit of an aspiring polyglot with no time to study, and too many languages on his plate in the first place.
--- Second thought: this video about high-speed rail in Canada is very true.