Yep. Giving up is smarter though when you realize you're doing something irredeemably stupid. The problem is, it either
a) should be obvious beforehand if you're doing something stupid (Very unrealistic *technical* assumptions both in NASP and X-33)
b) should be tested at such a small scale that dead ends don't prove so expensive and don't stop all other parallel progress by sucking all of the budget money
Yeah, that's not exactly what's happening, it was just to demonstrate the sunk cost fallacy. NASA won't ever do anything sustainable if it wants to operate a huge standing army just for its launchers.
Therefore your planning needs to be rational and open, and include a literature search.
There are ideas like Earth-Moon Lagrange point 2 for lunar staging (I think from the seventies already), that actually requires less delta vee than L1 or low Lunar orbit. But it is never even mentioned in NASA top level planning documents.
And countless other things - stuff that is happening inside NASA - that the decision makers are unwilling to listen or take into account.
Mike Griffin was the worst in his arrogance - and he's still loudly defending the Program of Record.
Sounds like Robert McNamara syndrome.
And at the same time there is rational and open architecture planning, there needs to be real research into new spaceflight technology, AND usage of metal-bent test stand and flying demonstrators that advance the state of the art.
And I agree about X-150. Sometimes the advances are not in energy efficiency (traditional rocketry optimization), but in better operability and workforce efficiency. You have to try and test how to operate rockets in cheaper ways. The original idea of X-vehicles was to try one or maybe a few techniques, to keep it small and to build multiple craft in case there were crashes (and there were). X-33 et al completely went against this - too many critical technologies in one. The composite tank materials could have been bench tested with a thousandth of the cost of the X-33 program - and would have been found unsuitable. This is not perfect hindsight, this is rational open planning. You don't start a billion dollar program just building blindly!
I don't think SSTO or higher ISP rockets are necessary for significantly lower cost to LEO. My best hunch would be two stage reusable lox-kerosene rockets (glide or vertical landing for first stage, same or parawing for the second stage). There is sufficient performance margin there with two stages with propulsion techology about 50 years old. It's a pretty straightforward way. It just requires evolution - multiple smaller X vehicles to develop the technologies to operational status, and then a requirement for enough flight rate that multiple different commercial vehicles will be economical per tonne in orbit.
If NASA would try to build a vehicle like that straight away, it would not be economical. You have to test what works first with smaller ones. Do the exploration.
