It is really sad that this design wasn't built. The Concorde was a great design, but obviously, you don't hit perfection on the first attempt. The Concorde "B" shows, that as with any design, it is important to have enough iterations to get real efficiency.
The Shuttle was a great design for the late 70ies. If it had at least a significant design iteration every 5-10 years, it could have been a bigger success. Similarly if the Concorde hat gotten 2-3 design iterations over its life, it could have been very successfull.
SpaceX is successful, because they are not trying to fly the initial F9 - it is said that they actually didn't built the exact same rocket twice, but always added small improvements.
I was explicitly talking about iterations after the production version. As the linked article shows, there were significant updates possible relative to the production version.
