The shuttle is aging. It is time to put up or shut up on a SSTO space plane, but there isn't one chance out of 10 gazillion that we're going to abandon manned space flight. The human mind doesn't work that way.
I was in the room when DCX was proposed to the Deputy for Technology at SDIO. The High Frontier guys were adamant that single stage to orbit was doable. This was the stuff of fiction in 1989, beyond our technology it was thought. Aerospace Corp. was commissioned to examine the numbers presented and found it to be plausible, but just barely. DCX was given to SDIO to protect it from the USAF who wasn't particularly interested in a program that might threaten some of their pet rocks plus it didn't have wings which is a cardinal sin to the boys in blue.
DCX was interesting but it was a low cost project with very little capability. Vertical lift off and descent was demonstrated adequately but its capability overall was very limited. Pete Conrad had a lot of fun with it. He used to wear his red "Artillery" socks on flight day for good luck. He essentially flew DCX by computer in a small van outfitted for that purpose. Of course he died a few years later in a motorcycle accident. A great loss for us all. Finally, the DCX-A (the project was taken over at NASA when they established the Reusable Launch Vehicle Office (I had transferred over to NASA by that point). The DCX-A flew a few times successfully with some upgraded hardware but eventually did a tip and burn on landing. It wasn't an inherent flaw in the hardware but rather a mistake made by the operations team on one of the hydraulically actuated "legs".
Then came the effort to move technology forward in the RLV world. With a very limited budget, by R&D standards given the scope of the project, NASA put out an RFP for candidate RLV systems. There were more bidders than expected but the top three US contractors offered the best proposals. One had wings, one was a lifting body, and one was modeled after DCX, i.e. vertical take off and landing.
The Lockheed version was the most stressing case from a technology perspective, although it was generally accepted that a two stage to orbit reusable vehicle was probably more achievable. There wasn't enough money to create a horse race, you couldn't afford to buy two contracts. In fact, it could be successfully argued that there wasn't enough money to buy one contract. After weeks of evaluation and debate it was decided that going after the most stressing case would bring more advances than chasing a lesser technology challenge. Thus was X-33 born.
Now you must remember that the X designation means that it is an experimental craft. Experimental craft fail on a routine basis for a variety of reasons. Experimental means just that.
Lockheed overreached in some ways. Not only was the technology experimental but the contract was too. It was to be an industry led partnership with the contractor putting some of their own money at risk. It was thought that this would provide incentive to the contractor to ensure success.
Well, we all know the outcome now. The composite tank failed in testing. There were other comparable problems that were solved but the incredibly complex design of the tank doomed, it seems, the effort. As an aside, I should note that the less heralded X-34 successfully built a composite kerosene tank that passed all testing and was certified. However, the X-34 failed because Marshall Space Flight Center was unable to provide an engine, GFE as called for in the contract, to meet with the airframe in a timely fashion. So yet another NASA project was wrecked on the shoals of underfunding and misplaced pride.
Had the X-33 been a success it is doubtful that SSTO would have been the number one choice for an objective launch system unless Norm Augustine worked his persuasive magic with DoD. An SSTO vehicle is essentially a thin skinned balloon loaded with propellant. It is huge and if left on orbit for any length of time suffers from exposure to micrometeor damage. It is constrained because of its size from docking with space station because of the laws of God, read physics.
So you see, your SSTO put up or shut up statement is a little more complicated than it would seem on the surface. However, your intent is well founded.